Defining dual diagnosis of mental illness and substance misus some methodological issues

Abstract

This paper discusses methodological issues arising in the initial stages of a larger epidemiological case–control study. Practitioners from both Generic Mental Health and Substance Misuse Services (n = 170) were asked to identify which of their clients, from a time-limited caseload (n = 2341), had comorbid mental health and substance misuse problems. Although practitioners were provided with a definition of ‘singly diagnosed’ and ‘dually diagnosed’, it became apparent that these definitions were applied pragmatically, depending on the nature of the client's primary problem and the agency they were presenting to. Issues raised include the time period in which a client was considered to have a concurrent mental health problem and substance misuse, how a ‘mental health problem’ was defined and whether a personality disorder should be categorized as a ‘mental health problem’. There was also some disagreement about whether clients who were being treated primarily by Substance Misuse Services, but were also taking prescribed antidepressants, implicitly had a ‘mental health problem’. We raise these methodological issues, as they have implications for determining the prevalence of ‘dual diagnosis’ and the subsequent provision of services.

Full text

Journal of Psychiatric and Mental Health Nursing, 2004, 11, 48 –54
48 © 2004 Blackwell Publishing Ltd
TODD J., GREEN G., HARRISON M., IKUESAN B. A., SELF C., BALDACCHINO A. &
SHERWOOD S. (2004) Journal of Psychiatric and Mental Health Nursing 11, 48–54
Defining dual diagnosis of mental illness and substance misuse: some
methodological issues
This paper discusses methodological issues arising in the initial stages of a larger epidemi-
ological case–control study. Practitioners from both Generic Mental Health and Substance
Misuse Services (n = 170) were asked to identify which of their clients, from a time-limited
caseload (n = 2341), had comorbid mental health and substance misuse problems. Although
practitioners were provided with a definition of ‘singly diagnosed’ and ‘dually diagnosed’,
it became apparent that these definitions were applied pragmatically, depending on the
nature of the client’s primary problem and the agency they were presenting to. Issues raised
include the time period in which a client was considered to have a concurrent mental health
problem and substance misuse, how a ‘mental health problem’ was defined and whether a
personality disorder should be categorized as a ‘mental health problem’. There was also
some disagreement about whether clients who were being treated primarily by Substance
Misuse Services, but were also taking prescribed antidepressants, implicitly had a ‘mental
health problem’. We raise these methodological issues, as they have implications for deter-
mining the prevalence of ‘dual diagnosis’ and the subsequent provision of services.
Keywords: definition, dual diagnosis, mental health, methodology, prevalence, substance
misuse
Accepted for publication: 6 August 2003
Blackwell Science, LtdOxford, UKJPMJournal of Psychiatric and Mental Health Nursing1365-2850Blackwell Publishing Ltd, 20041114854Original ArticleDefining dual diagnosis of mental illness and substance misuseJ. Todd
et al.
Defining dual diagnosis of mental illness and substance misuse:
some methodological issues
J. TODD1 bsc msc, G. GREEN2 bsc ma phd, M. HARRISON3 rmn dipn msc,
B. A. IKUESAN4 bsc msc pgd (addictions) cpsychol, C. SELF5 bsc d ip n ursing rn (mh),
A. BALDACCHINO6 md mrcpsych & S. SHERWOOD7 ba ma
1Senior Research Officer, and 2Reader, Department of Health and Human Sciences, University of Essex, Colchester, UK, 3Clinical
Nurse Specialist, 4Clinical Psychologist, and 5Community Psychiatric Nurse, North East Essex Drug and Alcohol Service, North
Essex Mental Health Partnership Trust (NEMHPT), Colchester, UK, 6Senior Lecturer in Addictions, Centre for Addiction Research
and Education, Department of Psychiatry, Ninewells Hospital, Dundee (previously North Essex Mental Health Partnership NHS
Trust (NEMHPT), Colchester, UK), 7Senior Research Officer, Department of Psychology, University of Essex, Colchester, UK
Correspondence:
J. Todd
Department of Health and
Human Sciences
University of Essex
Wivenhoe Park
Colchester
Essex CO4 3SQ
UK
E-mail: jtodd@essex.ac.uk
Introduction
The terms ‘dual diagnosis’ and ‘comorbidity’ are used
commonly and interchangeably to describe the coexist-
ence of one or more mental disorders in individuals who
also satisfy diagnostic criteria for a substance use disor-
der, or vice versa (Wittchen et al. 1996). In practice, the
term is specifically restricted to include severe mental ill-
ness (SMI) – psychosis, schizophrenia, bipolar affective
illness and substance misuse disorder. This is not a new
client group but a recently recognized one that has come
to prominence in the last 20 years with the closure of
large psychiatric institutions and the increasing prevalence
of drug misuse in the community. Comorbidity studies
are often conducted in three types of setting (Rassool
2002, p. 38):

© 2004 Blackwell Publishing Ltd, Journal of Psychiatric and Mental Health Nursing 11, 48–54 49
Defining dual diagnosis of mental illness and substance misuse
1high risk populations, which include clinical popu-
lations of substance misusers and/or those with SMI
and socially excluded groups such as those who are
homeless;
2general practice, where records provide data on present-
ing symptomatology, diagnostic impressions and pre-
scribing patterns of psychotropic medication; and
3general populations, where large-scale surveys examine
the distribution of comorbid disorders in the entire pop-
ulation and the detection of such individuals that have
not presented to treatment services.
Despite certain methodological difficulties, there is now
strong research evidence that the rate of substance misuse is
substantially higher among those with a mental illness,
compared with the general population. However, although
the increase in the number of individuals with a dual diag-
nosis has attracted considerable interest in recent years, the
impact of clinical and practical issues for practitioners both
in the mental health and addiction field has not yet been
fully recognized (Rassool 2002).
Background
Major community-based studies include the Epidemiologic
Catchment Area (ECA) study (Regier et al. 1990) which
surveyed over 19 000 individuals, across the United States
and found a lifetime prevalence rate for substance misuse
disorder of 16.7% (13.5% alcohol, 6.1% drug) for the gen-
eral population. Rates for those with schizophrenia, affec-
tive disorders and anxiety disorders were 47%, 32% and
23.7% respectively. For those with any drug (excluding
alcohol) disorder, more than half (53%) had one other
mental disorder, most commonly anxiety and affective
disorders. These rates are significantly higher than the
base rates found in the general population. The National
Comorbidity Survey (NCS) (Kessler et al. 1994) sampled
over 8000 individuals and found even higher rates of
comorbidity than the ECA. The National Longitudinal
Alcohol Epidemiological Survey (NLAES) (Grant 1995)
found a high level of association between alcohol and drug
use disorders.
The National Psychiatric Morbidity surveys of Great
Britain (Meltzer et al. 1995) found a clear relationship
between dependence on nicotine, alcohol and drugs and
other psychiatric morbidity. Most UK prevalence studies
have been limited to inner city London or very select SMI
populations. In London, Menezes et al. (1996) found a 1-
year prevalence rate among those with psychotic illness
for any substance misuse problem was 36.3% (31.6%
alcohol, 15.8% drug). Cantwell et al. (1999) found a 37%
12-month prevalence of drug use or drug or alcohol
misuse in a sample with first episode psychosis in
Nottingham.
The National Treatment Outcome Research Study
(NTORS), a prospective, multisite treatment outcome
study of drug users in the UK, examined substance use,
health and social problems of 1075 service users at intake
to 54 agencies. Psychological problems were common with
10% receiving inpatient hospital psychiatric treatment and
14% receiving community psychiatric treatment (for a
problem other than drug dependence) in the 2 years before
intake (Gossop et al. 1998). In the UK, the Office of Pop-
ulation Censuses and Surveys Household Survey estimated
the prevalence of alcohol and drug dependence among the
general population to be 5% and 2% respectively (Farrell
et al. 1998). Virgo et al. (2001) sampled clients from Adult
Mental Health (n = 708) and Addiction Services (n = 313).
They report comorbid SMI and substance abuse or depen-
dence in 12% of addictions, 12% of all adult mental health
patients, and 20% of adult mental health patients with SMI
in Eastern Dorset.
A number of issues have a bearing on prevalence esti-
mates and the location from which clients are sampled is of
particular interest when many studies are restricted to spe-
cific clinical groups, such as those with schizophrenia (e.g.
Buckley 1998) or inpatients (Dixon et al. 1998). Prevalence
estimates also rely on the ability of practitioners to identify
and classify clients with comorbid problems (and make
accurate records), and on how they define ‘dual diagnosis’.
Another problem with defining, as well as treating this cli-
ent group, is that historically, Substance Misuse and Men-
tal Health Services have evolved separately with few
services explicitly treating clients with both substance mis-
use and mental health problems. Different language and
models underpin services; drug and alcohol services them-
selves having undergone separate evolutions. Potential
problems are further compounded by different sources of
funding and different underlying philosophies of care (Leh-
man & Dixon 1995).
Clearly, it is hard to assess the exact levels of substance
misuse in both the general population and those with men-
tal health problems, and there can be significant obstacles
in detection because of the lack of a substance-specific
assessment in mental health settings. The Department of
Health has recently published a Dual Diagnosis Good
Practice Guide (DoH 2002) aimed at those who commis-
sion and provide mental health and substance misuse ser-
vices. This document states that the delivery of high
quality, patient-focused and integrated care for those with
a dual diagnosis should be delivered using mainstream
mental health services (DoH 2002). It is therefore impor-
tant that there is a clear understanding of what constitutes
a client who is dually diagnosed.

J. Todd et al.
50 © 2004 Blackwell Publishing Ltd, Journal of Psychiatric and Mental Health Nursing 11, 48–54
However, despite recognizing that there is a fundamen-
tal problem in the lack of a clear operational definition of
‘dual diagnosis’, these guidelines fail to clarify the situa-
tion, asking health care providers to develop their own
focused definitions of dual diagnosis, reflecting the target
group for whom their service is intended.
A further contentious issue is whether or not to include
personality disorder (PD) as a mental health problem. The
Good Practice Guidelines state that ‘it is not acceptable
for services to automatically exclude people with per-
sonality disorder. . . . for the purposes of the model,
personality disorder is seen as a separate dimension –
which can coexist with a mental health problem or a sub-
stance misuse problem, or both’ (DoH 2002, p. 7, section
1.2.3).
Our study suggests that, for health care practitioners,
making a dual diagnosis is a grey area with much room
for discussion. This paper, which is based on keywork-
ers’ assessment of their clients, deals with some of the
methodological issues which emerge when keyworkers
make an assessment of clients as singly or dually diag-
nosed. We raise issues which all service providers will
have to address and resolve when they generate their own
‘local’ definitions of dual diagnosis and calculate preva-
lence figures on which to base service provision to this
client group.
Methods
We report methodological issues arising from the early
stages of a larger case–control epidemiological study com-
paring clients with comorbid mental health and substance
misuse problems with singly diagnosed control groups
(data is being prepared for publication).
The study was carried out in a NHS Trust serving a
community in the east of England. Ethical approval was
obtained. The keyworkers constituted the sampling frame
for the study reported here. They encompassed the range
and diversity of health-care professionals who work across
the eastern sector of this Trust. The majority comprised
social workers, community psychiatric nurses (CPNs),
occupational therapists, psychiatrists, art therapists, men-
tal health nurses, clinical psychologists, and community
drug and alcohol workers.
The sample of keyworkers was obtained by generating
a list of all adult clients of a Mental Health Trust who
were receiving interventions under a Care Programme
Approach in November 2000. The Trust provides generic
mental health services (Community Mental Health Teams,
day services and day hospitals, inpatient units, psychother-
apy services and a Criminal Justice Mental Health Team),
and also a specialist drug and alcohol service for clients
who may or may not have mental health problems. Clients
who did not have a named keyworker were excluded. This
resulted in 2341 clients on caseload with keyworkers
(n = 170) whose average client caseload was 12 (range
1–53).
Keyworkers from Generic Mental Health Services were
contacted via a confidential letter, which enclosed a list of
their clients on caseload in November 2000. Keyworkers
from Drug and Alcohol Services had the same letter but
their list included their clients who were on caseload in
both the years 2000 and 1999.
Keyworkers were asked to assess whether each of their
listed clients was singly diagnosed or had comorbid mental
health and substance misuse problems (at a specified point
in time). We had previously undertaken a reliability study
examining the accuracy of keyworker assessments of
comorbidity. The level of agreement between keyworker
and ‘expert opinion’, based on examination of the client’s
notes, was 0.86 (Kappa 0.7), supporting the use of this
methodology in the main study.
In order to standardize the definition of ‘mental health
problem’ used in this study, an operational definition
(Table 1) was drawn up based on the Building Bridges
document (DoH 1995, p. 10). An operational definition of
‘substance misuse problem’ (Table 2) was based on DSM-
IV (APA 1994). Broad definitions reflected the range and
diversity of mental health and substance misuse problems
seen within this Trust. Clarification regarding the inclusion
of PD as a ‘mental health problem’ was sought by a minor-
ity of keyworkers. The decision was made to include PD as
a ‘mental health problem’ in order to provide a widely rep-
resentative sample, on the basis that previous research, for
example, the ECA Study (Regier et al. 1990) had found
significant prevalence of PD in a similar population to
ours.
Table 1
Study definition of ‘mental health problem’
A client with ‘mental health problems’ is defined by this research
project as being:
•an individual who meets criteria 1 (although they may not have a
named diagnosis)
•and who also fulfils at least one of the other factors listed below
1. are diagnosed as suffering from some sort of mental illness (or a
severe affective disorder, but including dementia)
2. suffer substantial disability as a result of their illness, such as an
inability to care for themselves independently or sustain
relationships or work
3. (a) are currently displaying florid symptoms or
(b) are suffering from a chronic, enduring condition
4. have suffered recurring crises leading to frequent admissions/
interventions
5. occasion significant risk to their own safety or that of others

© 2004 Blackwell Publishing Ltd, Journal of Psychiatric and Mental Health Nursing 11, 48–54 51
Defining dual diagnosis of mental illness and substance misuse
Depending on their diagnosis and the agency from
which they were sampled, clients were classified into one of
the following four study groups:
•Drug and Alcohol Services. Clients who had concur-
rent substance misuse and mental health problem(s);
•Drug and Alcohol Services. Clients who had a single
diagnosis of substance misuse only;
•Generic Mental Health Services. Clients (including
inpatients) who had a concurrent mental health and
substance misuse problem;
•Generic Mental Health Services. Clients (including
inpatients) who had a diagnosed mental health prob-
lem only. In total, 131 keyworkers (77% response
rate) provided data on 1314 clients.
Non-response was mainly because of keyworkers hav-
ing left the Trust; being on long-term study or sick leave;
being unable to recall clients; or failing to respond to the
initial letter or follow up contact. The prevalence of comor-
bid substance misuse and mental health problems, accord-
ing to keyworkers in the Drug and Alcohol Service was
29%. Prevalence of comorbid mental health problems and
substance misuse was 18% in the Generic Mental Health
Services. Overall prevalence of comorbidity in the com-
bined sample was 20%.
Discussion of methodological issues raised
during this stage of research
Examination of clients’ records at a later stage of this
research highlighted a number of inconsistencies in the
ways in which keyworkers from different disciplines had
initially defined ‘dual diagnosis’ and forms the basis for this
report, supported by brief case studies drawn from clients’
records.
Inconsistent diagnoses appear to rest on three issues
(discussed separately).
1The definition of a ‘mental health problem’ and ‘sub-
stance misuse’ as used by the practitioner and/or
researcher, together with the time-line in which a cli-
ent was deemed to have ‘active’ comorbidity.
2If being on prescribed antidepressants implicitly
denotes ‘having a mental health problem’.
3If a client with a PD should be classified as having a
‘mental health problem’.
Definition and time-line of comorbidity
The first issue to be addressed is the time-line of the diag-
nosis in which substance misuse and mental health prob-
lems are ‘actively comorbid’. Comorbidity can occur where
a substance misuse disorder is chronologically primary and
dominant, underlined by at least one psychiatric disorder.
Comorbidity can also be in the form of at least one psy-
chiatric disorder underlined by a substance misuse disorder.
Individuals with a dual diagnosis are a heterogeneous
group with various pathways in the development of this
diagnosis (Franey & Quirk 1996). They present many chal-
lenges for clinicians, especially where both disorders have
independent courses.
The brief case history below illustrates this issue.
The keyworker had originally defined this individual as
dually diagnosed. However, the research team decided that
this case was more consistent with a single diagnosis (men-
tal health problem only) in view of the lack of any active
drug misuse over the preceding 3 years.
Asking keyworkers for a diagnosis at a specific point in
time seemed straightforward. However, subsequent exam-
Client abc0384
This young adult female was described by her com-
munity mental health team (CMHT)-based key-
worker as dually diagnosed. There was long-standing
input from CMHT for anxiety and panic attacks,
together with a past history of amphetamine misuse,
but no ‘active’ drug use documented in the 3 years
prior to the research cut-off point. Prior to discharge,
she had been a regular client of the drug team, receiv-
ing support to enable her to maintain a drug-free
status.
Table 2
Study definition of ‘substance misuse disorder’
A client with ‘a substance misuse disorder’ is defined by this research
project as having:
EITHER
A combination of three or more of the following
1. A tolerance of the substance
2. Symptoms of withdrawal
3. Increasing amounts or greater frequency of use
4. Unsuccessful efforts to control use
5. Drug-seeking behaviour (e.g. travelling long distances or visiting
multiple doctors to obtain drugs)
6. Curtailing of social and/or occupational activities due to substance
use
7. Continued use despite knowledge of physical or psychological
problems caused
AND/OR
Substance use that results in a combination of one or more of the
following
1. Failure to fulfil role obligations
2. Use of drugs in dangerous situations (e.g. whilst driving or
operating machinery)
3. Recurrent legal/forensic problems
4. Continued use despite persistent social and interpersonal
problems caused by substance use

J. Todd et al.
52 © 2004 Blackwell Publishing Ltd, Journal of Psychiatric and Mental Health Nursing 11, 48–54
ination of client files in later stages of the study suggested
that clients were sometimes ‘categorized’ by their key-
worker according to a more global and holistic knowledge
of the client’s history rather than whether they had had a
mental health and/or substance misuse problem at a spe-
cific point in time.
Taking a lifetime overview of a client’s comorbidity may
provide artificially inflated prevalence figures. However,
taking a time-limited or ‘service year’ overview of com-
orbidity (as this study did) may produce artificially low
prevalence figures. This dilemma has implications when
conclusions are being drawn about the prevalence of dual
diagnosis in a specific population, especially if the dual
diagnosis time-frame is not explicitly stated. This observa-
tion could help to explain disparities in prevalence figures
across studies.
Use of prescribed antidepressants
The second issue to be addressed is with respect to the use
of antidepressants and the implicit assumption that these
drugs are used to treat a mental health problem – particu-
larly in clients with a primary substance misuse problem.
Practitioners with clients who have a primary mental
health diagnosis are well versed in working with individu-
als on prescribed psychotropic medication. If such a client
was also misusing drugs and/or alcohol, we noted that this
would generally be regarded as a clear indication of a dual
diagnosis.
Many clients of Drug and Alcohol Services are on com-
monly prescribed antidepressants, often via their general
practitioner (GP), and this type of ‘mental health prob-
lem’ could be regarded as an almost inevitable effect of
the client’s current life circumstances – the depressive ill-
ness, in part, because of a chaotic and disruptive lifestyle
which evolves out of regular substance misuse. However,
a client with a primary substance misuse problem who
was on GP prescribed antidepressants would not always
be described as ‘dually diagnosed’ by a drug or alcohol
worker. It is also unclear whether mental health pra-
ctitioners working with clients who primarily have
more serious and enduring mental health issues, would
regard a client of Drug and Alcohol Services, being
treated by a GP with antidepressants, as having a ‘mental
health problem’.
Interestingly, the NLAES (Grant 1995) published odds
ratios showing a significant association between drug use
and depression (7.2, current; 5.2, lifetime) and alcohol
abuse and depression (3.7, current; 3.6, lifetime).
The following case histories illustrate these two
points.
In these cases, the research team decided that the first
example was consistent with a dual diagnosis, as described
by the keyworker. However, the second example, although
defined as single diagnosis by the keyworker, was consid-
ered more consistent with a dual diagnosis of mental health
problems and comorbid substance misuse in view of the
previous and substantial history of depression and treat-
ment with antidepressants during the research time-line.
Personality disorder
The third issue to be addressed is whether or not to include
PD as a ‘mental health problem’. Substance misuse and PD
commonly co-occur, regardless of which disorder is viewed
as primary, and the two disorders are considered to main-
tain each other (Trull et al. 2000). Epidemiological studies
(e.g. ECA; Regier et al. 1990) have consistently found a
high prevalence of comorbidity for PDs and substance use
disorders.
The estimation of prevalence rates of PD vary from 44%
among those misusing alcohol to 79% among opiate users,
and many of these individuals may have more than one
type of PD (Rasool 2002, p. 53). Often the most complex
and challenging clients are those with a substance misuse
disorder, an Axis 1 disorder and an associated PD. These
are also the people most likely to be excluded from services.
Diagnostic uncertainty is a confounding factor in PD
with ‘contamination’ between diagnostic categories. Bor-
derline PD includes substance misuse as a criterion, and a
significant number of those misusing substances have ‘bor-
Client abc0164
An older male client of the substance misuse team
was described as dually diagnosed by the keyworker.
He had a prior note on file of having undergone a
CMHT assessment for depression but did not attend
any follow-up for treatment. He was on GP pre-
scribed antidepressants and had an active history of
misusing alcohol.
Client abc0166
This male client was described by his substance mis-
use keyworker as having a single diagnosis of ‘drug
misuse’. However, the file documented a previous his-
tory of depression and current use of prescribed anti-
depressants. In the service year, a GP had requested
‘psychiatric input due to a long history of difficulties
with social adjustment’. There was no recent evi-
dence of CMHT engagement, although that is not to
say that treatment wasn’t sought outside the Trust.

© 2004 Blackwell Publishing Ltd, Journal of Psychiatric and Mental Health Nursing 11, 48–54 53
Defining dual diagnosis of mental illness and substance misuse
derline’ features such as impulsivity and self-harm as part
of their range of maladaptive coping behaviours (Rasool
2002, p. 135).
Dual Diagnosis Guidelines (DoH 2002) regards PD as a
separate entity, which can coexist with a mental health or
substance misuse problem, or both. Personality disorder
was included in this study as indicative of a mental health
problem but it was clear that not all practitioners agreed.
Those who took part were drawn from a number of disci-
plines and their views about whether PD constituted a men-
tal health problem appeared to differ according to their
theoretical and clinical background.
The following brief case history is used to illustrate this
issue.
Examination of this client’s file found two assessments,
undertaken by different practitioners working within the
same service. One diagnosed a PD but a subsequent assess-
ment, by a different practitioner, stated that . . . ‘there was
no evidence of serious mental illness’. In accordance with
the keyworker’s original assertion and the researcher defi-
nition of ‘mental health problem’, this case remained in the
dual diagnosis group.
Conclusions
The issue of ‘diagnosis’ is important but as well as a diag-
nostic entity, it may be useful to regard ‘dual diagnosis’ as
a generic index of complexity (Rasool 2002, p. 134). The
term ‘dual diagnosis’ is more than just a label and the
importance of this label is that it can and does determine
service provision.
Depending on the assessing clinicians’ training and the-
oretical standpoint (which may vary between Substance
Misuse and Mental Health Teams), clients may attract a
diagnostic label, which could subsequently cause them to
fall outside the remit of either service – with its attendant
consequences. Whilst more UK research is needed into the
pattern and prevalence of comorbidity, there are still
widely acknowledged methodological difficulties in assess-
ing the prevalence of dual diagnosis, with marked varia-
tions between studies in reported prevalence rates (Franey
& Quirk 1996).
Client abc0718
This male client in his late 30s was described as
dually diagnosed by a keyworker from the substance
misuse team. The file documented a diagnosis of
‘abnormal personality complicated by a long history
of alcohol use’ but also stated that there was . . . ‘no
evidence of serious mental illness’.
Many clients of the Drug and Alcohol Services use anti-
depressants occasionally but service providers may not see
this as indicative of mental health problems. Likewise,
many clients with mental health problems may occasion-
ally misuse drugs but this use may not always be problem-
atic. Furthermore, diagnosis may change over time, in that
the drug user may develop serious mental health problems
or the mental health client may develop a serious substance
misuse problem and this change can occur even between
two data collection points within the same service year. The
operational use of concepts of substance use and misuse
rely heavily on particular cultures, ideology, aetiology and
clinical practice. Whether or not studies should include PD
as a ‘mental health problem’ looks set to be an ongoing
issue, as does the issue of whether to take a lifetime over-
view, as opposed to a time-limited view of comorbidity.
This preliminary work suggests that making a dual diag-
nosis is a grey area with much room for discussion. Whilst
this study has not attempted to provide the definitive def-
inition of what constitutes a dual diagnosis, the problems
and inconsistencies encountered may be comparable to
those seen among other Mental Health and Community
Drug and Alcohol Teams who provide a service for clients
with a dual diagnosis. Each team will develop their own
definition of dual diagnosis, as recommended in the Gov-
ernment Guide to Dual Diagnosis (DoH 2002), but this in
itself may cause dilemmas if practitioners or clients move
between different services.
This study has contributed to the ongoing debate of key
issues which need to be considered when ‘labelling’ clients
– either for the purposes of research or for ongoing service
provision.
Acknowledgments
The research team would like to thank the NHS Executive,
Eastern Region, for providing funding to carry out this
research; staff of the Mental Health Trust for their assis-
tance, especially the team at Medical Records and the Sub-
stance Misuse Service.
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L.L. & Goodwin F.K. (1990) Comorbidity of mental disorders
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Soc Psychiatry Psychiatr Epidemiol (2004) 39 :581 –587 DOI 10.1007/s00127-004-0790-0
■Abstract Background The concept of comorbid men-
tal health problems and substance misuse has gained
prominence in the last two decades, due in part to the
closure of large psychiatric hospitals and to the increas-
ing prevalence of drug use in the community. This client
group has a dual requirement for both medical and
social care needs and is at risk for social exclusion.
Methods A retrospective matched case-control study to
examine aspects of social exclusion between service
users who have comorbid diagnoses and those with a
single diagnosis. Samples were drawn from the service
users of a mental health Trust in the South-East of Eng-
land, from both Adult Mental Health (n = 400) and Drug
and Alcohol services (n =190). Data were collected from
Care Programme Approach assessment forms and
medical records. McNemar’s χ2and odds ratios via a
conditional logit regression model are used to test for
differences in the social exclusion indicators. Results
There were significant differences in social exclusion
between the comorbid and singly diagnosed clients of
the Adult Mental Health service, but differences were
less pronounced between the comorbid and singly diag-
nosed clients of the specialist Drug and Alcohol service.
Conclusions Recent Government policy advocates treat-
ing comorbid clients within mainstream mental health
services. Health care workers need to recognise the
likelihood of high levels of social exclusion among
clients with comorbid problems.
■Key words comorbidity – community treatment
settings – mental health – social exclusion – substance
misuse
Introduction
Dual diagnosis of mental illness and substance misuse
has long been recognised, but the real dimensions of
both the prevalence and the wider problems associated
with this client group have only been acknowledged
fairly recently. Usually the term ‘dual diagnosis’ refers to
individuals with a diagnosis of severe mental illness,
combined with alcohol and/or drug misuse, but ‘comor-
bidity’ (often used interchangeably with ‘dual diagnosis’
in the literature) more realistically reflects the variety
and severity of conditions which in combination with
substance misuse can have wide-ranging clinical, social
and legal implications. The literature has grown out of
contributions from the fields of mental health and sub-
stance misuse treatment, which traditionally have dif-
ferent philosophies about the responsibility of the
client/patient for their condition.The general trend sig-
nals an increasing comorbidity of substance use disor-
der and mental illness which impacts upon the range of
professionals working in mental health and substance
misuse in a variety of agencies in the statutory and non-
statutory sectors.This client group have problems relat-
ing to initial diagnosis, focus of intervention and general
management issues, risks of violence and self-harm,
risks of homelessness, and possibly poorer prognosis
(Johnson 1997).
The prevalence of drug and alcohol use among those
with severe mental health problems has been well docu-
mented by population studies in the US, e.g. the Epi-
demiological Catchment Area (ECA) adult population
study (Regier etal. 1990) and the National Comorbidity
ORIGINAL PAPER
J. Todd · G. Green · M.Harrison · B. A. Ikuesan · C. Self · D. J. Pevalin · A. Baldacchino
Social exclusion in clients with comorbid mental health
and substance misuse problems
Accepted: 19 February 2004
SPPE 790
J. Todd () · G. Green · D. J. Pevalin
Dept. of Health and Human Sciences
University of Essex
Wivenhoe Park
Colchester (Essex), CO4 3SQ,UK
Tel.: + 44-01206/873- 837
Fax: +44 -01206/873-765
E-Mail: jtodd@essex.ac.uk
M. Harrison · B. A.Ikuesan · C. Self · A.Baldacchino
North East Essex Drug & Alcohol Service
North Essex Mental Health Partnership Trust
Colchester, UK
A. Baldacchino
Dept. of Psychiatry
Ninewells Hospital
Dundee, UK

582
Survey (NCS) (Kendler et al. 1997). In the UK, major
studies include the Office for Population Census and
Survey (OPCS) national psychiatric comorbidity study
(Farrell et al.1998) which carried out three surveys sam-
pling from private households,institutional settings and
homeless populations. The National Treatment Out-
come Research Study (NTORS) sampled in-patient drug
and rehabilitation units (Marsden etal.2000). In the UK,
similar surveys, generally with inner-city populations,
have examined comorbidity in community-based men-
tal health and substance misuse services (e.g. Graham
et al.2001; Menezes etal. 1996).Keyworkers were used to
identify comorbidity in a sample drawn from commu-
nity mental health and substance misuse settings. Over
half (64 %) screened positive for comorbidity,indicating
that both substance misuse and mental health services
are managing and treating clients with complex needs
(Manning etal. 2002).
UK studies that sample community treatment set-
tings tend to focus on those with a diagnosis of severe
mental illness combined with alcohol and/or drug mis-
use, but these individuals may be quite different to those
with primary substance misuse who do not have severe
mental health problems. Researchers are beginning to
recognise the often complex clinical and social needs of
comorbid clients and taking a more social perspective.
In the UK, patients with schizophrenia and comorbid
substance misuse were younger, more likely to be male
and had shorter duration of illness. They had more po-
lice contact and increased self-reported needs, but oth-
erwise showed few differences when compared to their
singly diagnosed counterparts (Cantwell 2003). Patients
with functional psychosis and comorbid substance mis-
use had a greater number of unmet areas of need than
those with psychosis only, which included accommoda-
tion,daytime activity and social life (Wright etal. 2000).
Comorbid clients had more extensive and severe prob-
lems than those with a single diagnosis, posing more
risks to themselves and others, and making more de-
mands on services (in terms of crisis interventions)
(Virgo etal. 2001). Individuals with comorbid psychotic
illness and a substance use disorder were significantly
more likely than those with psychosis only to report any
history of committing an offence or recent hostile be-
haviour leading to the conclusion that comorbidity may
be an important factor in aggression and offending be-
haviour in those with comorbid conditions in inner-city
areas (Scott etal. 1998).
Relatively little empirical work has examined envi-
ronmental factors that may influence the demographic,
clinical and other characteristics of comorbidity. How-
ever, as the literature has evolved, there is now an ac-
knowledgement that psychosocial issues are critical in
attempts to understand and address this problem (e.g.
Drake etal. 2002). Employment, often considered to be
the cornerstone of social inclusion,is one of a number of
social exclusion factors studied in relation to comorbid-
ity. Strong links between substance misuse and unem-
ployment have been recognised (Home Office 1998) and
US studies have shown that substance misuse and men-
tal illness are linked to unemployment (Swartz etal.
2000).Work suggests that substance misuse may also be
important in assessing risk of violence among those
with severe mental illness and US research has found
higher rates of hostile behaviour (Bartels et al. 1991) and
legal problems (Lehman et al. 1993) in this group than
among those with psychosis alone. Comorbidity and
homelessness have been linked (e.g. Bebout etal. 1997;
Brunette et al.1998; Drake etal. 1991).In the US, patients
with comorbid mental illness and substance misuse who
were living in urban areas compared to those living in
rural areas had more involvement in the criminal justice
system, more homelessness, lower rates of marriage, ed-
ucational attainment and work (Mueser et al. 2001).
However, it has been found that effective treatment of
substance misuse among those with mental illness ap-
pears to reduce arrests and incarcerations, but not the
frequency of non-arrest encounters.Stable housing may
also reduce the likelihood and number of arrests (Clark
et al.1999).However, much of the literature continues to
focus on the complicating impact of substance misuse
on those who have a severe mental health problem,
rather than those with primary substance misuse and
comorbid mental health problems.
The extent and severity of co-existing mental illness
and substance misuse have been acknowledged in the
National Service Framework for Mental Health (DoH
1999) and a more recent document, ‘Dual Diagnosis
Good Practice Guidelines’ (DoH 2002), advocates deliv-
ering integrated care using mainstream mental health
services for this client group. It is, therefore, important
that generic mental health teams have the requisite ex-
pertise to recognise the range of clinical and social vul-
nerabilities exhibited by this client group.Using a retro-
spective case-control study, we report social exclusion
data for clients of community mental health and sub-
stance misuse services, comparing those with and with-
out comorbidity. We discuss the implications for treat-
ing this client group within mainstream mental health
services.
Subjects and methods
The study was carried out between November 2001 and December
2002 across adult community-based services provided by a NHS Trust
in the South-East of England. The geographical area, in terms of so-
cial composition,is quite diverse, encompassing a mix of relatively af-
fluent mainly rural areas and mixed urban areas,some of which have
high levels of social deprivation.
We sampled from two distinct populations: (1) clients with and
without comorbid substance misuse drawn from an Adult Mental
Health service (drawn from Community Mental Health teams, day
services and day hospitals, in-patient units plus small samples from
Psychotherapy services and the Criminal Justice Mental Health
Team), and (2) clients with and without comorbid mental health
problems drawn from a specialist Drug and Alcohol service.
The study was undertaken in two phases. The first phase was to
identify comorbid and singly diagnosed clients from a time-limited
caseload and calculate point-prevalence figures by agency. This was
undertaken by generating a list of all clients who were receiving in-

583
terventions under a Care Programme Approach in November 2000.
Clients younger than 18 or older than 65 were excluded, as were those
who did not have a named care co-ordinator or keyworker (hereafter
referred to as ‘keyworker’).
Keyworkers from adult mental health services were contacted via
a confidential letter, which enclosed a list of clients on caseload in No-
vember 2000. Keyworkers from drug and alcohol services had the
same letter,but their list included clients on caseload in both Novem-
ber 1999 and 2000 in order to generate a reasonable sample. Key-
workers were asked to assess whether each client was singly diag-
nosed or had comorbid mental health and substance misuse
problems at a specified point in time.We had previously undertaken
a reliability study examining the accuracy of keyworker assessments
of comorbidity and found that the level of agreement between key-
worker and expert opinion based on examination of the client’s notes
was 0.86 (Kappa 0.7), supporting the use of this methodology in the
main study (Todd etal. 2004).
In phase one, 131 from a possible 170 keyworkers provided data
on 1506 clients. Lost cases were primarily due to keyworkers having
left the Trust,being on long-term study or sick leave,being unable to
recall clients, or failing to respond to the initial letter or follow-up
contacts. In order to standardise the definition of ‘mental health prob-
lem’ used in this study, an operational definition (Box 1) was drawn
up, based on the Building Bridges document (DoH 1995). An opera-
tional definition of ‘substance misuse problem’ (Box2) was based on
DSM-IV (APA 1994). Broad definitions reflected the range and diver-
sity of mental health and substance misuse problems seen within the
Trus t. Pe rson ality disorder was included as a ‘mental health problem’
in order to provide a widely representative sample on the basis that
previous research (Regier etal. 1990) had found a significant preva-
lence of personality disorder in a similar population to the one we
were sampling.
The phase one sample,used to calculate prevalence figures,com-
prised clients of drug and alcohol services (n =331) together with
data from clients of adult mental health services (n = 1175). The
prevalence of comorbid mental health problems in the drug and al-
cohol clients was 29%. The prevalence of comorbid substance misuse
in the adult mental health service clients was 18%.
Clients were further classified into one of the following four study
groups, depending on diagnosis and agency from which they were
sampled:
Drug and Alcohol Services: clients who had concurrent substance
misuse and mental health problem(s).(DAS study group)
Drug and Alcohol Services: clients who had a single diagnosis of
substance misuse only (DAS control group)
Adult Mental Health Services: clients (including in-patients) who
had a concurrent mental health and substance misuse problem
(AMH study group)
Adult Mental Health Services: clients (including in-patients) who
had a diagnosed mental health problem only (AMH control
group).
For the second phase of the study,we drew a sample from these 1506
clients. Comorbid (cases) and singly diagnosed (controls) were
matched on gender and age ( ± 10 years for DAS clients and ± 6 years
for AMH clients). DAS clients were also matched on whether they
were drug, alcohol or polysubstance users. Data were then collected
from case notes, Care Programme Approach Assessment forms and
computer records. The final sample for each group was: DAS study
group n=89; DAS control group n=101; AMH study group n = 188;
and AMH control group n= 212.
The case-control matching for analysis was done in two ways: (1)
1:1 matching, and (2) K:K matching. This resulted in DAS (n= 80)
pairs matched 1:1. AMH (n =188) pairs matched 1:1. K-to-K (K:K)
matching involves any number of cases being matched with any num-
ber of controls. One-to-one (1:1) matching was required to calculate
McNemar’s χ2stat istic.The advantage of K:K matching is that all cases
and controls are used in the analyses and,therefore,all data are used
to estimate the odds ratios via a conditional logit model.
Results
The socio-demographic characteristics, mental health
problems and substance misuse of the study groups are
shown in Table 1.As the matching was done within each
agency, only comparisons between the comorbid and
singly diagnosed within each agency are appropriate.
The overall sample was predominantly male (almost
2:1) and almost exclusively white, with a mean age be-
tween 36 and 39.
Not surprisingly, alcohol and drug misuse were the
dominant problems in the DAS groups and mood
and/or anxiety problems were common in the AMH
groups.
In Table 2, comparisons are made between the DAS
comorbid (cases) and the singly diagnosed (controls).
Percentages, McNemar’s χ2from 1:1 matching,and odds
ratios with 95% CI from K:K matching are reported.
In this study, we operationalise ‘social exclusion’ us-
ing variables relating to employment,homelessness, ed-
ucation, isolation and contact with the criminal justice
system. The comorbid group has higher levels of exclu-
sion on all of the measures reported in Table 2.However,
while many of the differences are quite marked only two
Box 2 Study definition of ‘substance misuse disorder’
EITHER:
A combination of three or more of the following:
1. a tolerance of the substance
2. symptoms of withdrawal
3. increasing amounts or greater frequency of use
4. unsuccessful efforts to control use
5. drug-seeking behaviour (e. g. travelling long distances or visiting multiple
doctors to obtain drugs)
6. curtailing of social and/or occupational activities due to substance use
7. continued use despite knowledge of physical or psychological problems
caused
AND/OR:
Substance use that results in a combination of one or more of the following:
1. failure to fulfil role obligations
2. use of drugs in dangerous situations (e. g. whilst driving or operating
machinery)
3. recurrent legal/forensic problems
4. continued use despite persistent social and interpersonal problems caused
by substance use
Box 1 Study definition of ‘mental health problem’
Clients with ‘mental health problems’ are defined by this research project as
being:
individuals who meet criteria 1 (although they may not have a named
diagnosis)
and who also fulfil at least one of the other factors listed below:
1. are diagnosed as suffering from some sort of mental illness (or a severe af-
fective disorder, but including dementia)
2. suffer substantial disability as a result of their illness, such as an inability to
care for themselves independently or sustain relationships or work
3. (a) are currently displaying florid symptoms or
(b) are suffering from a chronic, enduring condition
4. have suffered recurring crises leading to frequent admissions/interven-
tions
5. occasion significant risk to their own safety or that of others

584
reach statistical significance and then only in the 1:1
matched analysis.
Table 3 shows the results for the comparisons be-
tween the AMH groups in a similar fashion to Table 2.
These results stand in marked contrast to those shown
in Table 2 in that there are significant differences on all
except one of the social exclusion measures. The AMH
comorbid group was significantly more likely to be so-
cially excluded than the singly diagnosed control group.
Discussion
Using a case-control design, clients from adult mental
health and substance misuse services, who had a range
of comorbid mental health and substance misuse prob-
lems were compared with singly diagnosed control
groups. We identified the extent to which indicators of
social exclusion, using variables relating to employ-
ment, homelessness, education, isolation and contact
with the criminal justice system, differed between the
groups.The comorbid groups were more likely to be dis-
% (except age) Drug and Alcohol Services Adult Mental Health Services
Comorbid Singly dx Comorbid Singly dx
n=89 n=101 n = 188 n = 212
Gender
Male 61 63 66 62
Female 39 37 34 38
Mean age (sd) 37 (9.5) 36 (10.9) 37 (11.2) 39 (11.5)
Ethnicity
White 100 98 99 98
Non-White – 2 1 2
Problem1, 2 (1 year)
Alcohol misuse 51 48 12 –
Drug misuse 35 47 2 –
Polysubstance misuse 15 5 2 –
Schizophrenia/psychotic 1 – 36 32
Mood/anxiety disorder 40 – 56 68
Personality disorder 18 – 23 11
Other disorders3–– 67
Substance(s)1(1-year)
Alcohol 62 52 70 –
Heroin 30 48 3 –
Cocaine/crack cocaine – 7 3 –
Amphetamines 6 3 10 –
Cannabis 10 4 33 –
Polysubstance use 8 1 4 –
Other substances410 5 8 –
1Categories of substance misuse and mental health problem were not mutually exclusive
2Not always formally assessed
3Somatoform; dissociative; sexual; gender; identity; impulse control; adjustment; eating
4Methadone (illicit); ecstasy, benzodiazepines, solvents and gases; DF118; hallucinogens/LSD/mushrooms
Table 1 Comparison of comorbid and singly diag-
nosed cases, by agency, on socio-demographics,
problem(s) treated, substance(s) misused (1-year)
Comorbid Singly dx χ2OR 95 % Cl
No fixed address (1 year) 17% 13 % 0.3 1.61 0.59–4.36
No fixed address (5 years) 29 % 26% 0.0 0.99 0.43–2.30
Employed 16% 27% 1.9 0.57 0.26–1.23
Completed secondary educationa89% 99% –––
Living alone 39 % 29 % 0.1 1.46 0.75–2.86
Engaged with legal system (1 year) 28 % 20 % 4.5* 1.90 0.89–4.09
Arrested (5 years) 42 % 27 % 4.5* 1.74 0.92–3.31
Any offence (5 years) 48 % 36 % 2.5 1.57 0.86–2.88
In prison (5 years) 28 % 21 % 1.0 1.43 0.66–3.10
* p < 0.05; aMajority had completed secondary education
Table 2 Comparison of comorbid and singly diag-
nosed cases on social exclusion variables for Drug and
Alcohol Services

585
advantaged in terms of social exclusion than their singly
diagnosed counterparts, but differences were far more
pronounced and statistically significant in the AMH
groups. We support previous UK studies using similar
populations (Cantwell 2003; Wright etal. 2000; Virgo
etal. 2001; Scott etal. 1998) and add to this literature
through the inclusion of Drug and Alcohol service
clients in our study.
■Limitations of the study
The sample was only representative of adults (aged
18–65) who were in contact with mental health or sub-
stance misuse services at a specific point in time. We
report aspects of social exclusion which focus on the
history of contact with the criminal justice system,
homelessness, living alone and employment data. This
study could be broadened by taking a wider view of ‘so-
cial exclusion’ perhaps through the examination of so-
cial networks in this client group. Although we con-
ducted the study using the best available information at
the time, we do recognise the potential unreliability of
data collected in routine practice, which in some cases
was incomplete.
Other UK studies have used keyworkers to identity
comorbidity (e. g.Manning et al.2002),but probably the
most important limitation of our study was that the
presence of comorbidity was dependent on retrospec-
tive diagnosis, verification and determination of case-
ness via keyworker assessment. The majority of clients
in the comorbid groups had undergone formal assess-
ment of both their substance misuse and mental health
problems; however, it is common for these agencies to
define the dominance of a disorder in terms of the first
treatment episode or the agency of first presentation
and our client composition was influenced by the crite-
ria the respective services were operating at the time.In
addition to these limitations, a sizeable minority of
clients had not had a formal assessment of their ‘sec-
ondary problem’ and it is important to be aware that
mental health and substance misuse agencies may be re-
ferring to different individuals when they discuss ‘co-
morbidity’ (Todd et al.2004).
■Strengths of the study
A major strength is the inclusion of clients, from both
agencies, with a broad and inclusive range of conditions,
using a wide and inclusive range of substances – in other
words,the typical clients of a UK mental health Trust.
In the UK literature, there are few empirical studies
which systematically examine and compare the social
characteristics of both singly diagnosed and comorbid
individuals. We examine the data from clients of sub-
stance misuse services who have less severe mental
health problems – those generally under-represented in
the comorbidity literature.
■Interpretation of findings
The main analysis suggests that those with comorbid
mental health and substance misuse – significantly so
within adult mental health services – are more likely to
be socially excluded (defined by this study as being
homeless, unemployed, having a lower educational level,
and isolated,i. e.living alone).This could be due to a lack
of stable housing, reflecting a chaotic lifestyle due to
substance misuse in addition to mental health problems.
Access to appropriate housing is a critical component of
social care for this client group.Epidemiological studies
have revealed that roughly 10–20 % of homeless people
suffer from severe mental illness and comorbid sub-
stance misuse and, as a group, are disproportionately at
risk of housing instability and homelessness (Drake
etal. 1991) which can exacerbate substance misuse and
mental health problems creating a deleterious cycle of
increased symptomatology, disability and exposure to
harsh living environments.
The comorbid groups were more likely to have been
in contact with the legal system than the control groups,
but, again, differences were only significant for Adult
Mental Health groups. Whilst treatment options in the
UK are now increasingly linked to the criminal justice
system (e.g. the compulsory treatment for drug prob-
lems via Drug Treatment and Testing Orders), this was
not so at the time of this study. Clients with comorbid
problems can face the additional burden of homeless-
Comorbid Singly dx χ2OR 95 % Cl
No fixed address (1 year) 15 % 5 % 9.5* 3.40 1.53–7.54
No fixed address (5 years) 28% 8 % 20.5* 4.51 2.25–9.04
Employed 14% 34% 15.2* 0.36 0.21–0.59
Completed secondary education 89 % 93 % 0.9 0.60 0.27–1.28
Living alone 51% 37 % 9.3* 1.85 1.20–2.83
Engaged with legal system (1 year) 15% 3 % 15.1* 4.73 1.94–11.5
Arrested (5 years) 33% 7 % 38.4* 9.41 4.04–21.9
Any offence (5 years) 35% 7 % 41.3* 10.05 4.32–23.4
In prison (5 years) 13 % 5% 7.0* 3.17 1.34–7.49
* p < 0.05
Table 3 Comparison of comorbid and singly diag-
nosed cases on social exclusion variables for Adult
Mental Health Services

586
ness or a transient lifestyle and the ensuing unstable en-
vironment can lead to contact with the criminal justice
system, both as an offender and as a victim. In some
towns and cities, there are laws that prohibit the home-
less from begging, loitering or sleeping in parks or on
the streets and, as a result, the homeless individual can
face arrest or harassment for simply trying to survive on
the streets.
Conclusions
This study suggests that substance misuse service users
with and without comorbid mental health problems
seem to be rather more similar to one another than men-
tal health service users with and without substance mis-
use problems.We have found significant differences in a
number of social exclusion measures between the co-
morbid and control group drawn from the Adult Mental
Health service, which supports previous research and
leads us to tentatively conclude that a comorbid diagno-
sis may be less of an added burden to a client with a pri-
mary substance misuse problem.It also suggests that the
association between substance misuse and social exclu-
sion is greater than that between mental health and so-
cial exclusion.The somewhat less marked differences in
social exclusion between comorbid and control groups
drawn from the Drug and Alcohol service are a new
source of information.This knowledge may be useful to
clinicians as the combination of substance misuse and
mental health problems is a significant public health
problem.
Government guidelines (DoH 2002) advocate treat-
ing clients with comorbid mental health and substance
misuse within mainstream mental health services. It is,
therefore,important that adult mental health teams have
the requisite expertise to treat clients who misuse sub-
stances and, in the long term, for regulatory bodies to
ensure that both mental health andsubstance misuse are
core components in the education of tomorrow’s generic
mental health workers. This study suggests that health-
care workers need to recognise the likelihood of high
levels of social exclusion among clients with comorbid
problems. It is likely that problems related to social ex-
clusion (e.g. a prison sentence) may have more impact
upon the client than their mental health problem per se.
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tions of mental and substance use disorders: A comparison of
single and dual diagnosis patients. J Nerv Ment Dis 181(6):
365–370
18. Manning VC, Strathdee G,Best D, Keaney F, McGillivray L,Wit-
ton J (2002) Dual diagnosis screening: preliminary findings on
the comparison of 50 clients attending community mental health
services and 50 clients attending community substance misuse
services. J Subst Use 7:221–228
19. Marsden J, Gossop M, Stewart D, Rolfe A, Farrell M (2000) Psy-
chiatric symptoms among clients seeking treatment for drug de-
pendence. Intake data from the National Treatment Outcome
Research Study.Br J Psychiatry 176:285–9
20. Menezes PR, Johnson S, Thornicroft G, Marshall J, Prosser D,
Bebbington P, Kuipers E (1996) Drug and alcohol problems
among individuals with severe mental illness in south London.
Br J Psychiatry 168(5):612–619
21. Meuser KT, Essock SM, Drake RE, Wolfe RS, Frisman L (2001)
Rural and urban differences in patients with a dual diagnosis.
Schizophrenia Research 48:93–107
22. Regier DA, Farmer ME, Rae DS, Locke BZ, Keith SJ, Judd LL,
Goodwin FK (1990) Comorbidity of mental disorders with alco-
hol and other drug abuse: results from the Epidemiologic Catch-
ment Area (ECA) study. JAMA 264:2511–2518
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Substance misuse and risk of aggression and offending among
the severely mentally ill.Br J Psychiatry 172(4):345–350
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eficiaries for drug addiction and alcoholism. Arch Gen Psychiatr
57:701–707
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Sherwood S (2004) Defining dual diagnosis of mental illness and
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use. Soc Psychiatry Psychiatr Epidemiol 35:297–304

Dual diagnosis: A case control study (Data collection sheet2)
1
DATA COLLECTION SHEET
SECTION 1
DEMOGRAPHIC INFORMATION
Study ID code
abc prefix denotes year 2000 clients, xyz prefix denotes 1999 clients
Study Group  Drug & Alcohol Service (DAS) comorbid
 Drug & Alcohol Service (DAS) singly diagnosed
 Adult Mental Health (AMH) comorbid
 Adult Mental Health (AMH) singly diagnosed
Service Year  1999
 2000
Gender  Male
 Female
Age (5Y bands)  18-22
 23-27
 28-32
 33-37
 38-42
 43-47
 48-52
 53-57
 58 and older
Referral source (for events in service year)
 GP
 Self-referral
 Drug and Alcohol Services
 Justice System (including probation or Criminal Justice Mental Health Team)
 Relative/friend
 Adult Mental Health
 Hospital (general or psychiatric)
 Social services

Dual diagnosis: A case control study (Data collection sheet2)
2
 Unknown
 Other (describe) __________________
Ethnic Group
 White (European)
 White (non-European)
 Black British
 Afro Caribbean
 Black Caribbean
 Black Other
 Chinese
 Indian
 Pakistani
 Bangladeshi
 Other ethnic group
 Unknown
Number of addresses (service year)
 One
 Two
 Three or more
Homeless/risk of no fixed address (NFA) (service year)
Any temporary accommodation e.g. Bed & Breakfast, squat, hostel, night shelter or
'vulnerable address'
 Yes
 No
 Unknown
Vulnerably housed/homeless (last 5 years)
Any temporary accommodation e.g. Bed & Breakfast, squat, hostel, night shelter or
'vulnerable address'
 Yes
 No
 Unknown
Marital Status (service year)
 Single
 Married
 Separated

Dual diagnosis: A case control study (Data collection sheet2)
3
 Divorced
 Widowed
 Other (describe) ___________________
 Unknown
Housing (service year)
 Multiple occupancy
 Owner-occupier
 Supported housing
 Private rented
 Council/HA
 Prison
 In-patient
 Parent/relative/carer
 Temporary
 Caravan
 Bedsit/lodgings
 NFA
 Partner’s house
 Job-related accommodation
 Unknown
 Other (describe) ________________
Household
 Multiple occupancy
 Partner and child(ren)
 Partner
 Child(ren)
 Parent/relative/carer
 House share
 Prison
 In-patient
 Living alone
 NFA
 Other (describe) ______________
 Unknown

Dual diagnosis: A case control study (Data collection sheet2)
4
Children
 No children
 One
 Two
 Three or more
 Unknown
Living arrangement for any children
 No children
 In care/adopted/fostered
 Grown up
 Co-resident
 With ex-partner
 Split residency
 Unknown
 Deceased
 Other (describe) _____________
Qualifications (highest level)
 No qualifications
 Apprenticeship/trade
 Vocational (NVQ etc)
 CSE
 GCSE/O Levels
 A Levels (equivalent)
 Degree
 Unknown
Educational level
 Left education system early
 Completed formal education (age 15-16)
 Higher Education (age 16+)
 Unknown
Employment (service year)
 Full time employment
 Self employed
 Temporary/casual/part time
 Full time housewife/parent

Dual diagnosis: A case control study (Data collection sheet2)
5
 Voluntary work
 Retired
 Unemployed
 Never worked
 Not working on medical grounds
 Full time carer
 Unknown
 Student
 Other (describe) __________________________________
Pattern of employment (last 5Y)
 Continuous employment
 Some sustained employment
 In and out of work
 No paid employment
 Unknown
Main source of income (service year)
 Employment
 Part-time employment
 Benefits
 Pension/private income
 Supported by partner/parents
 Unknown
 Crime
 Other (describe) __________________
Social class
(Description of present or last known occupation) ___________________________
 Never worked
 Class I (professional/managerial)
 Class II (skilled/white-collar skilled)
 Class III (clerical – unskilled non-manual)
 Class IVa (skilled manual)
 Class V (unskilled manual)
 Army /ex-army
 Unknown

Dual diagnosis: A case control study (Data collection sheet2)
6
SECTION 2
PERSONAL AND FAMILY INFORMATION
Family history of mental illness (blood relative/partner)
 No
 Yes
 Unknown
Family history of substance misuse (blood relative/partner)
 No
 Yes
 Unknown
Childhood experience(s)
ADHD/dyslexia/learning difficulties Yes No Unknown
In care/fostered/adopted Yes No Unknown
Disrupted/disturbed childhood Yes No Unknown
Persistent truancy/conduct /expelled Yes No Unknown
Psychiatric dx/intervention in childhood Yes No Unknown
At risk (service year)
Harm to self
(deliberate self harm/suicide/overdose) Yes No Unknown
Self neglect Yes No Unknown
Harm to others Yes No Unknown
Lifetime history of sexual/physical/emotional abuse
Yes No Unknown

Dual diagnosis: A case control study (Data collection sheet2)
7
SECTION 3
MEDICAL/PSYCHIATRIC HISTORY AND SUBSTANCE
MISUSE
PRIMARY Diagnosis – service year
(describe if unable to classify) __________________________
 Alcohol dependence/misuse
 Drug dependence/misuse
 Polysubstance dependence/misuse
 Substance related disorder (organic)
 Schizophrenia/other psychotic disorders
 Mood disorders (depressive, bipolar)
 Anxiety/phobia/panic disorder/OCD
 Somatoform/Dissociative Disorders (e.g. pain, body dysmorphic, hypochondriasis)
 Sexual and gender identity disorders
 Eating disorders
 Impulse control disorders
 Adjustment disorders
 Personality disorders
(paranoid, schizoid, schizotypal, antisocial, borderline, histrionic, narcissistic,
avoidant, dependent, obsessive-compulsive)
SECONDARY Diagnosis - service year
Clinician Diagnosis – service year
(describe if unable to classify) _______________________________
 NO SECONDARY DIAGNOSIS
 Alcohol dependence/misuse
 Drug dependence/misuse
 Polysubstance dependence/misuse
 Substance related disorder (organic)
 Schizophrenia/other psychotic disorders
 Mood disorders (depressive, bipolar)
 Anxiety/phobia/panic disorder/OCD
 Somatoform/Dissociative Disorders (e.g. pain, body dysmorphic, hypochondriasis)
 Sexual and gender identity disorders
 Eating disorders
 Impulse control disorders

Dual diagnosis: A case control study (Data collection sheet2)
8
 Adjustment disorders
 Personality disorders
(paranoid, schizoid, schizotypal, antisocial, borderline, histrionic, narcissistic,
avoidant, dependent, obsessive-compulsive)
Physical health (previous 5 years) Describe ____________________________
 Nothing of note
 One chronic condition
 More than one chronic condition
 Unknown
Prescribed medication (service year)
 Nothing of note
 Anti-depressants/anti-anxiety drugs
 Anti-psychotics
 Medication for acute/chronic physical health
 Other (describe) ___________________
 Unknown
Main substance used or misused (service year)
 NO SUBSTANCE(S) USED
 Alcohol
 Heroin
 Methadone (illicit)
 Methadone (prescribed)
 Opiates (unspec)
 Stimulants (unspec)
 Cocaine/crack
 Amphetamines
 Ecstasy
 Cannabis
 Benzodiazepines
 Barbiturates
 Solvents/gases
 DF118 (Dihydrocod)
 Hallucinogens
 LSD
 Magic Mushrooms
 Prescribed Methadone

Dual diagnosis: A case control study (Data collection sheet2)
9
 Prescription drugs
 Polydrugs
 Unknown
 Other (describe) _______________
Secondary substance used or misused (service year)
 NO SECONDARY SUBSTANCE(S) USED
 Alcohol
 Heroin
 Methadone (illicit)
 Methadone (prescribed)
 Opiates (unspec)
 Stimulants (unspec)
 Cocaine/crack
 Amphetamines
 Ecstasy
 Cannabis
 Benzodiazepines
 Barbiturates
 Solvents/gases
 DF118 (Dihydrocod)
 Hallucinogens
 LSD
 Magic Mushrooms
 Prescribed Methadone
 Prescription drugs
 Polydrugs
 Unknown
 Other (describe) _______________
Substance use/misuse (lifetime history)
 Nothing of note
 Alcohol
 Drugs
 Polysubstances
 Unknown

Dual diagnosis: A case control study (Data collection sheet2)
10
SECTION 4
FORENSIC HISTORY
Legal Status (service year)
 Nothing of note
 In Police custody
 In court
 On probation
 On bail
 Out on License
 In Prison
 Unknown
Arrested (service year/last 5 years)
 Nothing of note
 Arrested once or twice
 Multiple arrests
 Unknown
Main category of offence (service year/last 5 years)
 Nothing of note
 Theft/robbery/shoplifting
 Drug/alcohol related offence(s)
 Assault/threatening
 Domestic violence
 Sexual offence
 Motoring offence/drink driving
 Weapon possession
 Arson
 Other (describe) ______________________________

Dual diagnosis: A case control study (Data collection sheet2)
11
Secondary offence (service year/last 5 years)
 Nothing of note
 Theft/robbery/shoplifting
 Drug/alcohol related offence(s)
 Assault/threatening
 Domestic violence
 Sexual offence
 Motoring offence/drink driving
 Weapon possession
 Arson
 Other (describe) ______________________________
In prison (service year/last 5 years)
 No
 Once or twice
 Multiple custodial sentences
 Unknown
Assessed by Forensic Psychiatrist (service year/last 5 years)
 No
 Yes
 Unknown
Family forensic history (service year/last 5 years)
 No
 Yes
 Unknown

Dual diagnosis: A case control study (Data collection sheet2)
12
SECTION 5
ENGAGEMENT WITH SERVICES
PRIMARY CARE
Registered with GP
 Yes
 No
COMMUNITY EVENTS
(I.e seen by keyworker or care co-coordinator)
• Substance Misuse Services - Alcohol Team (service year)
 No engagement recorded
 Engagement
 Engagement (not quantified in records)
 Number of events attended
DNA’s
 Engagement in previous 5 years
 Yes
 Nothing on file
• Substance Misuse Service - Drug Team (service year)
 No engagement recorded
 Engagement
 Engagement (not quantified in records)
 Number of events attended
DNA’s
 Engagement in previous 5 years
 Yes
 Nothing on file

Dual diagnosis: A case control study (Data collection sheet2)
13
• Needle/syringe exchange services used (service year/previous 5Y)
 Yes
 No/not applicable
• Substance Misuse Services or GP Methadone Programme (service
year/previous 5 years)
 Yes
 No/not applicable
• On prescribed methadone (from one of above) (service year)
 Yes
 No/not applicable
• Community/prison detox (service year/previous 5Y)
 Nothing on file
 GP/home detox
 Prison detox
 Self detox
 Combination of detox’s
 Other (describe) ____________
• Adult Mental Health Service events (service year)
 No engagement recorded
 Engagement
 Engagement (not quantified in records)
 Number of events attended
 DNA’s
Engagement in previous 5 years
 Yes
 Nothing on file

Dual diagnosis: A case control study (Data collection sheet2)
14
• In-patient detox events
Drug/alcohol detox (service year)  Yes  Nothing on file
Drug/alcohol detox (last 5 years)  Yes  Nothing on file
 In-patient mental health events
Mental health (service year)  Yes  Nothing on file
Mental health (last 5 years)  Yes  Nothing on file
MENTAL HEALTH ACT DETENTIONS
• Detained under Section of Mental Health Act (service year)
Nothing on file detained once detained more than once
• Detained under Section of Mental Health Act (previous 5 years)
Nothing on file detained once detained more than once
OUT-PATIENT CARE EVENTS
• Out patient events for substance misuse and/or mental health
problems (service year)
 No engagement recorded
 Engagement
 Engagement (not quantified in records)
 Number of events attended
 DNA’s
Engagement in previous 5 years
 Yes
 Nothing on file
DAY HOSPITAL (service year)
 No engagement recorded
 Engagement

Dual diagnosis: A case control study (Data collection sheet2)
15
 Engagement (not quantified in records)
 Number of events attended
 DNA’s
Engagement in previous 5 years
 Yes
 Nothing on file
OTHER EVENTS
• Residential Rehab facilities – substance misuse
Attended (service year or previous 5 years) Yes Nothing on file
Details ______________________________________________________
• Residential Rehab facilities – mental health
Attended (service year or previous 5 years) Yes Nothing on file
Details ______________________________________________________
• Emergency Events
‘Out of hours’ (unscheduled/weekend or crisis stabilization)
Events (service year or previous 5 years)
 No
 Yes
 Unknown
Details ______________________________________________
NON-STATUTORY SERVICES (engagement in service yr or previous 5Y)
• Alcohol Project Yes Nothing on file
• MIND (mental health) Yes Nothing on file
• Substance Misuse drop-in Yes Nothing on file
• Counselling (not through Trust) Yes Nothing on file
• Youth Enquiry Service (local) Yes Nothing on file
• Church-based Health Project Yes Nothing on file

Dual diagnosis: A case control study (Data collection sheet2)
16
• Vocational (partnership with DAS) Yes Nothing on file
• Housing/drop-in for substance misusers Yes Nothing on file
• Day-centre/support for sub misusers Yes Nothing on file
• Alcoholics Anonymous/Narcotics
Anonymous (self help groups) Yes Nothing on file
Other non-stat services attended (describe) ____________________________
Work/vocational service (run by Trust) for mental health clients
Yes Nothing on file
Client Status (service year)
 Alive
 Deceased

Dual diagnosis: A case control study (Data Codebook)
1
DATA CODEBOOK
--------------------------------------------------------------------------------
id id code
--------------------------------------------------------------------------------
type: string (str7)
unique values: 590 missing "": 0/590
examples: "abc0582"
"abc1031"
"abc1607"
"abc2314"
--------------------------------------------------------------------------------
studygp study group
--------------------------------------------------------------------------------
type: numeric (byte)
range: [1,4] units: 1
unique values: 4 missing .: 0/590
tabulation: Freq. Numeric Label
89 1 DAS comorbid
101 2 DAS singly dx
188 3 AMH comorbid
212 4 AMH singly dx
--------------------------------------------------------------------------------
refso referral source for documented events in service year
--------------------------------------------------------------------------------
type: numeric (byte)
range: [1,99] units: 1
unique values: 7 missing .: 0/590
tabulation: Freq. Numeric Label
376 1 GP
40 2 self/relative/friend
57 3 inter agency
34 4 Justice system
17 5 hospital
13 6 social services
53 99 unknown
--------------------------------------------------------------------------------
gender gender
--------------------------------------------------------------------------------
type: numeric (byte)
range: [1,2] units: 1
unique values: 2 missing .: 0/590
tabulation: Freq. Numeric Label
374 1 male
216 2 female

Dual diagnosis: A case control study (Data Codebook)
2
--------------------------------------------------------------------------------
age age in 5-year bands
--------------------------------------------------------------------------------
type: numeric (byte)
range: [1,9] units: 1
unique values: 9 missing .: 0/590
tabulation: Freq. Numeric Label
41 1 18 to 22
76 2 23 to 27
118 3 28 to 32
92 4 33 to 37
74 5 38 to 42
65 6 43 to 47
56 7 48 to 52
40 8 53 to 57
28 9 58 and over
--------------------------------------------------------------------------------
ethgp ethnic groups (collapsed)
--------------------------------------------------------------------------------
type: numeric (byte)
range: [1,2] units: 1
unique values: 2 missing .: 0/590
tabulation: Freq. Numeric Label
582 1 white
8 2 non-white
--------------------------------------------------------------------------------
maritst marital status
--------------------------------------------------------------------------------
type: numeric (byte)
range: [1,3] units: 1
unique values: 3 missing .: 0/590
tabulation: Freq. Numeric Label
320 1 single
124 2 married
146 3 sep/div/wid
--------------------------------------------------------------------------------
housing housing status
--------------------------------------------------------------------------------
type: numeric (byte)
range: [1,99] units: 1
unique values: 6 missing .: 0/590
tabulation: Freq. Numeric Label
93 1 owner occupier
237 2 council/rented
57 3 prison/in-patient/sup
99 4 others house

Dual diagnosis: A case control study (Data Codebook)
3
33 5 vulnerable/nfa
71 99 unknown
--------------------------------------------------------------------------------
numaddr number of addresses in service year
--------------------------------------------------------------------------------
type: numeric (byte)
range: [1,2] units: 1
unique values: 2 missing .: 0/590
tabulation: Freq. Numeric Label
484 1 one address
106 2 two or more
--------------------------------------------------------------------------------
nfanow homeless/risk nfa (service yr)
--------------------------------------------------------------------------------
type: numeric (byte)
range: [0,99] units: 1
unique values: 3 missing .: 0/590
tabulation: Freq. Numeric Label
511 0 no
64 1 yes
15 99 unknown
--------------------------------------------------------------------------------
nfa5y vulnerably hsed/homeless (5 yr)
--------------------------------------------------------------------------------
type: numeric (byte)
range: [0,99] units: 1
unique values: 3 missing .: 0/590
tabulation: Freq. Numeric Label
430 0 no
108 1 yes
52 99 unknown
--------------------------------------------------------------------------------
numbch number of children ever
--------------------------------------------------------------------------------
type: numeric (byte)
range: [1,5] units: 1
unique values: 5 missing .: 0/590
tabulation: Freq. Numeric Label
109 1 one
104 2 two
102 3 three or more
273 4 none
2 5 unknown

Dual diagnosis: A case control study (Data Codebook)
4
--------------------------------------------------------------------------------
childliv living arrangements for children (service year)
--------------------------------------------------------------------------------
type: numeric (byte)
range: [1,8] units: 1
unique values: 8 missing .: 0/590
tabulation: Freq. Numeric Label
32 1 in care/adopted/fostered
85 2 grown up
78 3 with ex-partner
100 4 co-resident
13 5 split residency
7 6 deceased
271 7 no children
4 8 unknown
--------------------------------------------------------------------------------
qualif qualification (highest)
--------------------------------------------------------------------------------
type: numeric (byte)
range: [1,8] units: 1
unique values: 8 missing .: 0/590
tabulation: Freq. Numeric Label
18 1 apprenticeship/trade
5 2 vocational
20 3 cse
112 4 gcse/o level
47 5 a level or equivalent
27 6 degree
261 7 none
100 8 unknown
--------------------------------------------------------------------------------
educlev educational level
--------------------------------------------------------------------------------
type: numeric (byte)
range: [0,3] units: 1
unique values: 4 missing .: 0/590
tabulation: Freq. Numeric Label
41 0 did not complete secondary
education
403 1 secondary education completed
80 2 higher education completed
66 3 unknown
--------------------------------------------------------------------------------
employst employment status
--------------------------------------------------------------------------------
type: numeric (byte)
range: [1,13] units: 1

Dual diagnosis: A case control study (Data Codebook)
5
unique values: 9 missing .: 0/590
tabulation: Freq. Numeric Label
328 1 unemployed
91 2 employed
48 3 part time/temporary/casual work
47 5 parent/carer
6 7 never worked
21 8 retired
37 9 not working on medical grounds
5 11 unknown
7 13 student
--------------------------------------------------------------------------------
employpa pattern of employment (last 5y)
--------------------------------------------------------------------------------
type: numeric (byte)
range: [2,6] units: 1
unique values: 5 missing .: 0/590
tabulation: Freq. Numeric Label
382 2 no recent paid employment
31 3 in and out of work
82 4 some sustained employment
86 5 continuous employment
9 6 unknown
--------------------------------------------------------------------------------
income main source of income
--------------------------------------------------------------------------------
type: numeric (byte)
range: [1,9] units: 1
unique values: 4 missing .: 0/590
tabulation: Freq. Numeric Label
124 1 employment
363 2 benefits
65 3 other
38 9 unknown
--------------------------------------------------------------------------------
mhfam hx of mental illness in family
--------------------------------------------------------------------------------
type: numeric (byte)
range: [1,99] units: 1
unique values: 2 missing .: 0/590
tabulation: Freq. Numeric Label
137 1 yes
453 99 unknown

Dual diagnosis: A case control study (Data Codebook)
6
--------------------------------------------------------------------------------
sudfam hx of substance misuse in family
--------------------------------------------------------------------------------
type: numeric (byte)
range: [1,99] units: 1
unique values: 2 missing .: 0/590
tabulation: Freq. Numeric Label
105 1 yes
485 99 unknown
--------------------------------------------------------------------------------
learning childhood exp - adhd/dyslexia/ld
--------------------------------------------------------------------------------
type: numeric (byte)
range: [1,99] units: 1
unique values: 2 missing .: 0/590
tabulation: Freq. Numeric Label
37 1 yes
553 99 unknown
--------------------------------------------------------------------------------
carefost childhood exp - in care/fostered/adopted
--------------------------------------------------------------------------------
type: numeric (byte)
range: [1,99] units: 1
unique values: 2 missing .: 0/590
tabulation: Freq. Numeric Label
65 1 yes
525 99 unknown
--------------------------------------------------------------------------------
disrchil childhood exp - disrupted/behavioural probs
--------------------------------------------------------------------------------
type: numeric (byte)
range: [1,99] units: 1
unique values: 2 missing .: 0/590
tabulation: Freq. Numeric Label
92 1 yes
498 99 unknown
--------------------------------------------------------------------------------
truancy childhood exp - truancy/conduct/expel
--------------------------------------------------------------------------------
type: numeric (byte)
range: [1,99] units: 1
unique values: 2 missing .: 0/590

Dual diagnosis: A case control study (Data Codebook)
7
tabulation: Freq. Numeric Label
95 1 yes
495 99 unknown
--------------------------------------------------------------------------------
psychild childhood exp - psychiatric dx/intervention
--------------------------------------------------------------------------------
type: numeric (byte)
range: [1,99] units: 1
unique values: 2 missing .: 0/590
tabulation: Freq. Numeric Label
66 1 yes
524 99 unknown
--------------------------------------------------------------------------------
selfharm at risk of dsh/overdose taken (service year)
--------------------------------------------------------------------------------
type: numeric (byte)
range: [1,99] units: 1
unique values: 2 missing .: 0/590
tabulation: Freq. Numeric Label
172 1 yes
418 99 unknown
--------------------------------------------------------------------------------
selfnegl at risk of self neglect (service year)
--------------------------------------------------------------------------------
type: numeric (byte)
range: [1,99] units: 1
unique values: 2 missing .: 0/590
tabulation: Freq. Numeric Label
61 1 yes
529 99 unknown
--------------------------------------------------------------------------------
violence at risk of endangering others (service year)
--------------------------------------------------------------------------------
type: numeric (byte)
range: [1,99] units: 1
unique values: 2 missing .: 0/590
tabulation: Freq. Numeric Label
60 1 yes
530 99 unknown

Dual diagnosis: A case control study (Data Codebook)
8
--------------------------------------------------------------------------------
hxabuse history of sexual/physical/mental abuse
--------------------------------------------------------------------------------
type: numeric (byte)
range: [1,99] units: 1
unique values: 2 missing .: 0/590
tabulation: Freq. Numeric Label
156 1 yes
434 99 unknown
--------------------------------------------------------------------------------
dx1 index problem being treated for in service year
--------------------------------------------------------------------------------
type: numeric (byte)
range: [1,20] units: 1
unique values: 9 missing .: 0/590
tabulation: Freq. Numeric Label
95 1 alcohol dependence/misuse
80 2 drug dependence/misuse
19 3 polysubstance dependence/misuse
134 5 schizophrenia/other psychotic
disorders
171 6 mood disorder(s)
51 7 anxiety disorders (incl ptsd)
8 11 eating disorders
19 15 personality disorders
13 20 other
--------------------------------------------------------------------------------
dx2 additional problem being treated for in service year
--------------------------------------------------------------------------------
type: numeric (byte)
range: [1,20] units: 1
unique values: 9 missing .: 429/590
tabulation: Freq. Numeric Label
21 1 alcohol dependence/misuse
3 2 drug dependence/misuse
3 3 polysubstance dependence/misuse
2 5 schizophrenia/other psychotic
disorders
42 6 mood disorder(s)
22 7 anxiety disorders (incl ptsd)
2 11 eating disorders
64 15 personality disorders
2 20 other
429 .

Dual diagnosis: A case control study (Data Codebook)
9
--------------------------------------------------------------------------------
physhlth physical health (5y)
--------------------------------------------------------------------------------
type: numeric (byte)
range: [1,99] units: 1
unique values: 2 missing .: 0/590
tabulation: Freq. Numeric Label
139 1 chronic condition
451 99 unknown
--------------------------------------------------------------------------------
presmed prescribed medications (service year))
--------------------------------------------------------------------------------
type: numeric (byte)
range: [1,6] units: 1
unique values: 5 missing .: 0/590
tabulation: Freq. Numeric Label
83 1 no
320 2 anti-depressants/anti-anxiety
164 3 anti-psychotic/anti manic drugs
22 4 medication for acute/chronic
physical health
1 6 unknown
--------------------------------------------------------------------------------
mainsub main substance used (service year)
--------------------------------------------------------------------------------
type: numeric (byte)
range: [1,22] units: 1
unique values: 9 missing .: 0/590
tabulation: Freq. Numeric Label
217 1 alcohol
83 2 heroin/opiates
4 6 cocaine/crack
10 7 amphetamines
45 9 cannabis
214 18 no substances used
4 19 polysubstance
7 21 misuse prescription drugs
6 22 other
--------------------------------------------------------------------------------
additsub additional substance used (service year)
--------------------------------------------------------------------------------
type: numeric (byte)
range: [1,22] units: 1
unique values: 9 missing .: 0/590
tabulation: Freq. Numeric Label
26 1 alcohol

Dual diagnosis: A case control study (Data Codebook)
10
6 2 heroin/opiates
8 6 cocaine/crack
16 7 amphetamines
30 9 cannabis
474 18 no additional substances used
13 19 polysubstance
5 21 misuse prescription drugs
12 22 other
--------------------------------------------------------------------------------
sublife substance use (lifetime history)
--------------------------------------------------------------------------------
type: numeric (byte)
range: [1,4] units: 1
unique values: 4 missing .: 0/590
tabulation: Freq. Numeric Label
181 1 alcohol
123 2 drugs
114 3 polysubstance
172 4 nothing recorded
--------------------------------------------------------------------------------
legalsys legal status (service year)
--------------------------------------------------------------------------------
type: numeric (byte)
range: [1,6] units: 1
unique values: 5 missing .: 0/590
tabulation: Freq. Numeric Label
505 1 none
31 2 case pending/bail
30 3 on probation
20 5 in custody
4 6 unknown
--------------------------------------------------------------------------------
arrested arrested (service year/previous 5y)
--------------------------------------------------------------------------------
type: numeric (byte)
range: [1,4] units: 1
unique values: 3 missing .: 0/590
tabulation: Freq. Numeric Label
429 1 no
155 2 yes
6 4 unknown
--------------------------------------------------------------------------------
offence1 main offence (serviceyear/previous 5y)
--------------------------------------------------------------------------------
type: numeric (byte)
range: [1,99] units: 1

Dual diagnosis: A case control study (Data Codebook)
11
unique values: 8 missing .: 0/590
tabulation: Freq. Numeric Label
52 1 theft/shoplifting/robbery
30 2 drug/alcohol related
42 3 assault/threatening
15 7 motoring offence/drink driving
3 8 weapon possession
10 9 other
432 10 none
6 99 unknown
--------------------------------------------------------------------------------
offence2 secondary offence (service year/previous 5y)
--------------------------------------------------------------------------------
type: numeric (byte)
range: [1,99] units: 1
unique values: 8 missing .: 0/590
tabulation: Freq. Numeric Label
20 1 theft/shoplifting/robbery
16 2 drug/alcohol related
22 3 assault/threatening
7 7 motoring offence/drink driving
6 8 weapon possession
8 9 other
505 10 none
6 99 unknown
--------------------------------------------------------------------------------
prison prison sentences (service year/previous 5y)
--------------------------------------------------------------------------------
type: numeric (byte)
range: [1,4] units: 1
unique values: 4 missing .: 0/590
tabulation: Freq. Numeric Label
506 1 no
54 2 one or two
24 3 more than two
6 4 unknown
--------------------------------------------------------------------------------
forenpsy assessed by forensic psychiatrist(service year/previous 5y)
--------------------------------------------------------------------------------
type: numeric (byte)
range: [1,99] units: 1
unique values: 2 missing .: 0/590
tabulation: Freq. Numeric Label
22 1 yes
568 99 unknown

Dual diagnosis: A case control study (Data Codebook)
12
--------------------------------------------------------------------------------
forenfam family forensic history
--------------------------------------------------------------------------------
type: numeric (byte)
range: [1,99] units: 1
unique values: 2 missing .: 0/590
tabulation: Freq. Numeric Label
17 1 yes
573 99 unknown
--------------------------------------------------------------------------------
gp registered with GP (service yr)
--------------------------------------------------------------------------------
type: numeric (byte)
range: [1,1] units: 1
unique values: 1 missing .: 0/590
tabulation: Freq. Numeric Label
590 1 yes
--------------------------------------------------------------------------------
dasa1 DAS alcohol (service year) events
--------------------------------------------------------------------------------
type: numeric (byte)
range: [0,1] units: 1
unique values: 2 missing .: 0/590
tabulation: Freq. Numeric Label
466 0 no
124 1 yes
--------------------------------------------------------------------------------
dasa2 events attended DAS alcohol (service year)
--------------------------------------------------------------------------------
type: numeric (byte)
range: [0,22] units: 1
unique values: 21 missing .: 13/590
mean: .97747
std. dev: 3.03873
percentiles: 10% 25% 50% 75% 90%
0 0 0 0 3
--------------------------------------------------------------------------------
dasa3 events DNA'd DAS alcohol (service year)
--------------------------------------------------------------------------------
type: numeric (byte)
range: [0,6] units: 1
unique values: 7 missing .: 13/590

Dual diagnosis: A case control study (Data Codebook)
13
tabulation: Freq. Value
525 0
32 1
6 2
6 3
4 4
3 5
1 6
13 .
--------------------------------------------------------------------------------
dasa4 engagement DAS alcohol (previous 5y)
--------------------------------------------------------------------------------
type: numeric (byte)
range: [0,1] units: 1
unique values: 2 missing .: 0/590
tabulation: Freq. Numeric Label
516 0 no
74 1 yes
--------------------------------------------------------------------------------
dasd1 DAS drug (service year) events
--------------------------------------------------------------------------------
type: numeric (byte)
range: [0,1] units: 1
unique values: 2 missing .: 0/590
tabulation: Freq. Numeric Label
490 0 no
100 1 yes
--------------------------------------------------------------------------------
dasd2 events attended DAS drug (service year)
--------------------------------------------------------------------------------
type: numeric (byte)
range: [0,25] units: 1
unique values: 20 missing .: 9/590
mean: .827883
std. dev: 2.8632
percentiles: 10% 25% 50% 75% 90%
0 0 0 0 2
--------------------------------------------------------------------------------
dasd3 events DNA'd DAS drug (service year)
--------------------------------------------------------------------------------
type: numeric (byte)
range: [0,12] units: 1
unique values: 9 missing .: 9/590

Dual diagnosis: A case control study (Data Codebook)
14
tabulation: Freq. Value
533 0
29 1
4 2
9 3
2 4
1 5
1 6
1 8
1 12
9 .
--------------------------------------------------------------------------------
dasd4 engagement DAS drug (previous 5y)
--------------------------------------------------------------------------------
type: numeric (byte)
range: [0,1] units: 1
unique values: 2 missing .: 0/590
tabulation: Freq. Numeric Label
510 0 no
80 1 yes
--------------------------------------------------------------------------------
needle local needle/syringe exchange services used (now or last 5y)
--------------------------------------------------------------------------------
type: numeric (byte)
range: [0,1] units: 1
unique values: 2 missing .: 0/590
tabulation: Freq. Numeric Label
561 0 no
29 1 yes
--------------------------------------------------------------------------------
methprog local drug service methadone programme attended (now or last 5y)
--------------------------------------------------------------------------------
type: numeric (byte)
range: [0,1] units: 1
unique values: 2 missing .: 0/590
tabulation: Freq. Numeric Label
511 0 no
79 1 yes
--------------------------------------------------------------------------------
onmeth on prescribed methadone from local drug service/GP
--------------------------------------------------------------------------------
type: numeric (byte)
range: [1,2] units: 1
unique values: 2 missing .: 0/590
tabulation: Freq. Numeric Label

Dual diagnosis: A case control study (Data Codebook)
15
69 1 yes
521 2 no
--------------------------------------------------------------------------------
detox community and/or other detox (service year/ last 5y)
--------------------------------------------------------------------------------
type: numeric (byte)
range: [0,5] units: 1
unique values: 5 missing .: 0/590
tabulation: Freq. Numeric Label
506 0 no
53 1 gp/home detox
13 3 prison detox
10 4 self detox
8 5 various detox
--------------------------------------------------------------------------------
amh1 AMH (service year) events
--------------------------------------------------------------------------------
type: numeric (byte)
range: [0,1] units: 1
unique values: 2 missing .: 0/590
tabulation: Freq. Numeric Label
230 0 no
360 1 yes
--------------------------------------------------------------------------------
amh2 events attended AMH (service year)
--------------------------------------------------------------------------------
type: numeric (int)
range: [0,101] units: 1
unique values: 57 missing .: 8/590
mean: 9.13402
std. dev: 14.1498
percentiles: 10% 25% 50% 75% 90%
0 0 2 14 26
--------------------------------------------------------------------------------
amh3 events DNA'd AMH (service year)
--------------------------------------------------------------------------------
type: numeric (byte)
range: [0,23] units: 1
unique values: 18 missing .: 8/590
mean: .986254
std. dev: 2.55672
percentiles: 10% 25% 50% 75% 90%
0 0 0 1 3

Dual diagnosis: A case control study (Data Codebook)
16
--------------------------------------------------------------------------------
amh4 engagement AMH (previous 5y)
--------------------------------------------------------------------------------
type: numeric (byte)
range: [0,1] units: 1
unique values: 2 missing .: 0/590
tabulation: Freq. Numeric Label
271 0 no
319 1 yes
--------------------------------------------------------------------------------
inpsub1 in-patient drug/alcohol detox in service year
--------------------------------------------------------------------------------
type: numeric (byte)
range: [0,1] units: 1
unique values: 2 missing .: 0/590
tabulation: Freq. Numeric Label
557 0 no
33 1 yes
--------------------------------------------------------------------------------
inpsub2 in-patient drug/alcohol detox in previous 5y
--------------------------------------------------------------------------------
type: numeric (byte)
range: [0,1] units: 1
unique values: 2 missing .: 0/590
tabulation: Freq. Numeric Label
543 0 no
47 1 yes
--------------------------------------------------------------------------------
inpmh1 in-patient for mental health in service year
--------------------------------------------------------------------------------
type: numeric (byte)
range: [0,1] units: 1
unique values: 2 missing .: 0/590
tabulation: Freq. Numeric Label
497 0 no
93 1 yes

Dual diagnosis: A case control study (Data Codebook)
17
--------------------------------------------------------------------------------
inpmh2 in-patient for mental health in previous 5y
--------------------------------------------------------------------------------
type: numeric (byte)
range: [0,1] units: 1
unique values: 2 missing .: 0/590
tabulation: Freq. Numeric Label
402 0 no
188 1 yes
--------------------------------------------------------------------------------
mhdetai1 detentions under mental health act (service year)
--------------------------------------------------------------------------------
type: numeric (byte)
range: [0,2] units: 1
unique values: 3 missing .: 0/590
tabulation: Freq. Numeric Label
547 0 no
30 1 detained once
13 2 detained more than once
--------------------------------------------------------------------------------
mhdetai2 detentions under mental health act (previous 5y)
--------------------------------------------------------------------------------
type: numeric (byte)
range: [0,2] units: 1
unique values: 3 missing .: 0/590
tabulation: Freq. Numeric Label
499 0 no
28 1 detained once
63 2 detained more than once
--------------------------------------------------------------------------------
outp1 outpatient events (service year)
--------------------------------------------------------------------------------
type: numeric (byte)
range: [0,1] units: 1
unique values: 2 missing .: 0/590
tabulation: Freq. Numeric Label
333 0 no
257 1 yes

Dual diagnosis: A case control study (Data Codebook)
18
--------------------------------------------------------------------------------
outp2 events attended as outpatient (service year)
--------------------------------------------------------------------------------
type: numeric (byte)
range: [0,16] units: 1
unique values: 12 missing .: 2/590
mean: 1.2415
std. dev: 2.01937
percentiles: 10% 25% 50% 75% 90%
0 0 0 2 4
--------------------------------------------------------------------------------
outp3 events dna'd as outpatient (service year)
--------------------------------------------------------------------------------
type: numeric (byte)
range: [0,4] units: 1
unique values: 5 missing .: 1/590
tabulation: Freq. Value
475 0
62 1
37 2
14 3
1 4
1 .
--------------------------------------------------------------------------------
outp4 events as out-patient (previous 5y)
--------------------------------------------------------------------------------
type: numeric (byte)
range: [0,1] units: 1
unique values: 2 missing .: 1/590
tabulation: Freq. Numeric Label
330 0 no
259 1 yes
1 .
--------------------------------------------------------------------------------
dayhosp1 day hospital events (service year)
--------------------------------------------------------------------------------
type: numeric (byte)
range: [0,1] units: 1
unique values: 2 missing .: 0/590
tabulation: Freq. Numeric Label
517 0 no
73 1 yes

Dual diagnosis: A case control study (Data Codebook)
19
--------------------------------------------------------------------------------
dayhosp2 day hospital events attended (service year)
--------------------------------------------------------------------------------
type: numeric (byte)
range: [0,83] units: 1
unique values: 22 missing .: 6/590
mean: 1.08219
std. dev: 6.47068
percentiles: 10% 25% 50% 75% 90%
0 0 0 0 0
--------------------------------------------------------------------------------
dayhosp3 events dna'd at day hospital
--------------------------------------------------------------------------------
type: numeric (byte)
range: [0,17] units: 1
unique values: 10 missing .: 6/590
mean: .181507
std. dev: 1.07263
percentiles: 10% 25% 50% 75% 90%
0 0 0 0 0
--------------------------------------------------------------------------------
dayhosp4 day hospital events (previous 5y)
--------------------------------------------------------------------------------
type: numeric (byte)
range: [0,1] units: 1
unique values: 2 missing .: 0/590
tabulation: Freq. Numeric Label
530 0 no
60 1 yes
--------------------------------------------------------------------------------
rehab residential rehab attended (now and last 5y)
--------------------------------------------------------------------------------
type: numeric (byte)
range: [0,2] units: 1
unique values: 3 missing .: 0/590
tabulation: Freq. Numeric Label
520 0 no
37 1 drug/alcohol rehab
33 2 mental health rehab

Dual diagnosis: A case control study (Data Codebook)
20
--------------------------------------------------------------------------------
emerg hospital A&E or out of hours or crisis stabilisation
--------------------------------------------------------------------------------
type: numeric (byte)
range: [0,1] units: 1
unique values: 2 missing .: 0/590
tabulation: Freq. Numeric Label
460 0 no
130 1 yes
--------------------------------------------------------------------------------
localcpro attend voluntary local alcohol project(now and last 5y)
--------------------------------------------------------------------------------
type: numeric (byte)
range: [0,1] units: 1
unique values: 2 missing .: 0/590
tabulation: Freq. Numeric Label
551 0 no
39 1 yes
--------------------------------------------------------------------------------
mind attend voluntary local MIND centre (now and last 5y)
--------------------------------------------------------------------------------
type: numeric (byte)
range: [0,1] units: 1
unique values: 2 missing .: 0/590
tabulation: Freq. Numeric Label
541 0 no
49 1 yes
--------------------------------------------------------------------------------
locsubcon attend voluntary sub. misuse, drop in, counselling/alternative (now
and last 5y)
--------------------------------------------------------------------------------
type: numeric (byte)
range: [0,1] units: 1
unique values: 2 missing .: 0/590
tabulation: Freq. Numeric Label
521 0 no
69 1 yes

Dual diagnosis: A case control study (Data Codebook)
21
--------------------------------------------------------------------------------
counsel attend local counselling services not provided by AMH (now and
last 5y)
--------------------------------------------------------------------------------
type: numeric (byte)
range: [0,1] units: 1
unique values: 2 missing .: 0/590
tabulation: Freq. Numeric Label
530 0 no
60 1 yes
--------------------------------------------------------------------------------
ythcouns attend voluntary support/counselling 16-25 year olds (now and
last 5y)
--------------------------------------------------------------------------------
type: numeric (byte)
range: [0,1] units: 1
unique values: 2 missing .: 0/590
tabulation: Freq. Numeric Label
581 0 no
9 1 yes
--------------------------------------------------------------------------------
dichrh church-based drop-in projects (now and last 5y)
--------------------------------------------------------------------------------
type: numeric (byte)
range: [0,1] units: 1
unique values: 2 missing .: 0/590
tabulation: Freq. Numeric Label
582 0 no
8 1 yes
--------------------------------------------------------------------------------
vocstatser AMH vocational service
--------------------------------------------------------------------------------
type: numeric (byte)
range: [0,1] units: 1
unique values: 2 missing .: 0/590
tabulation: Freq. Numeric Label
562 0 no
28 1 yes

Dual diagnosis: A case control study (Data Codebook)
22
--------------------------------------------------------------------------------
traingd training & employment guidance
--------------------------------------------------------------------------------
type: numeric (byte)
range: [0,1] units: 1
unique values: 2 missing .: 0/590
tabulation: Freq. Numeric Label
575 0 no
15 1 yes
--------------------------------------------------------------------------------
commassoc community organisation for sub. misuse, housing, social
--------------------------------------------------------------------------------
type: numeric (byte)
range: [0,1] units: 1
unique values: 2 missing .: 0/590
tabulation: Freq. Numeric Label
589 0 no
1 1 yes
--------------------------------------------------------------------------------
gendaycen general/housing/support day centre
--------------------------------------------------------------------------------
type: numeric (byte)
range: [0,1] units: 1
unique values: 2 missing .: 0/590
tabulation: Freq. Numeric Label
589 0 no
1 1 yes
--------------------------------------------------------------------------------
aana self help support groups (now and last 5y)
--------------------------------------------------------------------------------
type: numeric (byte)
range: [0,1] units: 1
unique values: 2 missing .: 0/590
tabulation: Freq. Numeric Label
571 0 no
19 1 yes

Dual diagnosis: A case control study (Data Codebook)
23
--------------------------------------------------------------------------------
other other voluntary organisations (now and last 5y)
--------------------------------------------------------------------------------
type: numeric (byte)
range: [0,1] units: 1
unique values: 2 missing .: 0/590
tabulation: Freq. Numeric Label
565 0 no
25 1 yes
--------------------------------------------------------------------------------
status alive or deceased in the service yr
--------------------------------------------------------------------------------
type: numeric (byte)
range: [1,2] units: 1
unique values: 2 missing .: 0/590
tabulation: Freq. Numeric Label
576 1 alive
14 2 deceased
--------------------------------------------------------------------------------
case Case/control identifier for DD:SD matching - DD=case
--------------------------------------------------------------------------------
type: numeric (byte)
range: [0,1] units: 1
unique values: 2 missing .: 0/590
tabulation: Freq. Value
313 0
277 1
--------------------------------------------------------------------------------
gpid1 Group identifier for DD:SD 1:1 matching
--------------------------------------------------------------------------------
type: numeric (int)
range: [10001,21124] units: 1
unique values: 268 missing .: 54/590
mean: 17699.8
std. dev: 4647.79
percentiles: 10% 25% 50% 75% 90%
10027 11035.5 20054.5 21057.5 21098

Dual diagnosis: A case control study (Data Codebook)
24
--------------------------------------------------------------------------------
gpid2 Group identifier for DD:SD K:K matching
--------------------------------------------------------------------------------
type: numeric (int)
range: [10001,21124] units: 1
unique values: 268 missing .: 0/590
mean: 17456.7
std. dev: 4724.99
percentiles: 10% 25% 50% 75% 90%
10027.5 11033 20049 21055 21096