www.thelancet.com Vol 379 January 7, 2012 71
Lancet 2012; 379: 71–83
See Editorial page 2
See Perspectives pages 20 and 22
This is the second in a Series of
three papers about addiction
King’s College London, National
Addiction Centre, London, UK
(Prof J Strang MD); Department
of Community Medicine and
Health Care, University of
Connecticut School of
Medicine, Farmington, CT, USA
(Prof T Babor PhD); Carnegie
Mellon University, Heinz
College, Pittsburgh, PA, USA,
and Qatar Campus, Doha, Qatar
(Prof J Caulkins PhD); Centre for
Applied Research in Mental
Health and Addictions
(CARMHA), Faculty of Health
Sciences, Simon Fraser
University, Vancouver, BC, and
Drug policy and the public good: evidence for eff ective
John Strang, Thomas Babor, Jonathan Caulkins, Benedikt Fischer, David Foxcroft, Keith Humphreys
Debates about which policy initiatives can prevent or reduce the damage that illicit drugs cause to the public good are
rarely informed by scientifi c evidence. Fortunately, evidence-based interventions are increasingly being identifi ed that
are capable of making drugs less available, reducing violence in drug markets, lessening misuse of legal pharmaceuticals,
preventing drug use initiation in young people, and reducing drug use and its consequences in established drug users.
We review relevant evidence and outline the likely eff ects of fuller implementation of existing interventions. The
reasoning behind the fi nal decisions for action might be of a non-scientifi c nature, focused more on what the public
and policy-makers deem of value. Nevertheless, important opportunities exist for science to inform these deliberations
and guide the selection of policies that maximise the public good.
Illicit drugs are a substantial threat to the public good,
not only because they adversely aff ect public health,
but also because they can generate crime, disorder, family
breakdown, and community decay. The diverse policies
and programmes to ameliorate these problems vary
substantially in their eff ectiveness. Here we review
eff ective interventions to draw attention to the drug-
control policies available to governments, in much the
same ways as evidence has contributed to debates about
more eff ective tobacco and alcohol policies.
Building on the fi rst paper in this series,1 which assessed
the extent to which illicit drug use contributes to the global
burden of disease, we critically assess the scientifi c basis of
interventions intended to prevent or at least minimise the
damage that illicit drugs do to the public good. We examine
the quality of evidence for diff erent policies, estimate
the likely magnitude of their eff ects, assess potential
unintended consequences, and identify promising areas
for future investment into research and interventions. We
can thus help policy makers make informed decisions
about which policy options will maximise the public good.
By the public good we refer to social benefi ts such as better
public health, reduced crime, and greater stability and
quality of life for families and neigh bourhoods. Contem-
porary drug-related public policy attempts to promote the
public good through a broad range of administrative
actions designed to prevent the initiation of drug use by
non-users, help heavy drug users change their behaviour
or reduce the consequences of their drug use, and control
the supply of illicit drugs (and the supply of diverted
prescription drugs used for non-medical purposes)
through laws, regulations, and enforcement.
Much public debate in drug policy is only minimally
informed by scientifi c evidence. Values and political
processes (eg, voting) are important drivers of drug
policy, but evidence of eff ectiveness and cost-eff ectiveness
can help the public and policy makers to select policies
that best achieve agreed goals.
For the formulation of drug policy, coordination of
diff erent methods of study and analysis from diff erent
scientifi c subject areas is needed. Interpretation of this
evidence will depend not only on study design and
magnitude of eff ect, but also on the relevance and
generalisability of the fi ndings. In addition to the
assessment of new interventions and strategies, exam-
ination of the costs and benefi ts of policy measures
that might mistakenly be assumed eff ective is also
• Drug policy should aim to promote the public good by improving individual and
public health, neighbourhood safety, and community and family cohesion, and by
• The eff ectiveness of most drug supply control policies is unknown because little
assessment has been done, and very little evidence exists for the eff ectiveness of
alternative development programmes in source countries.
• Supply controls can result in higher drug prices, which can reduce drug initiation and
use but these changes can be diffi cult to maintain.
• Wide-scale arrests and imprisonments have restricted eff ectiveness, but drug testing
of individuals under criminal justice supervision, accompanied by specifi c,
immediate, and brief sentences (eg, overnight), produce substantial reductions in
drug use and off ending.
• Prescription regimens minimise but do not eliminate non-medical use of psychoactive
prescription drugs. Prescription monitoring systems can reduce inappropriate prescribing.
• Screening and brief intervention programmes have, on average, only small eff ects, but
can be widely applied and are probably cost-eff ective.
• The collective value of school, family, and community prevention programmes is
appraised diff erently by diff erent stakeholders.
• The provision of opiate substitution therapy for addicted individuals has strong
evidence of eff ectiveness, although poor quality of provision reduces benefi t.
Peer-based self-help organisations are strongly championed and widely available, but
have been poorly researched until the past two decades.
• Health and social services for drug users covering a range of treatments, including needle
and syringe exchange programmes, improve drug users’ health and benefi t the broader
community by reducing transmission of and mortality due to infectious disease.
www.thelancet.com Vol 379 January 7, 2012
Centre for Addiction and
Mental Health, Toronto, ON,
Canada (Prof B Fischer PhD);
Oxford Brookes University,
(Prof D Foxcroft PhD); and
Department of Veterans
Aff airs, Stanford University,
Palo Alto, CA, USA
(Prof K Humphreys PhD)
Prof J Strang, Addiction Sciences
Building, 4 Windsor Walk,
Denmark Hill, London,
SE5 8BB, UK
We examine evidence of good scientifi c quality that can
inform decision-making about drug policies that can be
introduced, modifi ed, expanded, reduced, or stopped.
This includes scientifi c evidence for the likely benefi ts to
the public good. Some of the evidence comes from
randomised trials and quasi-experimental designs with
similar control conditions.
We also consider other types of evidence when
randomised controlled trials could not be implemented
or would be politically challenging to implement. This
includes natural policy experiments (ie, observational
studies done to assess the eff ect of policy interventions)
and time-series analyses. In some policy domains, such
studies provide the best available scientifi c evidence. For
each of the fi ve broad policy approaches that we discuss,
we fi rst identify the relevant activity, and also the objective
Illicit drugs are ultimately consumer goods, typically
produced and distributed through illegal markets
operated by people motivated by profi t. The goal of supply
control programmes is to reduce access to drugs by
interfering with drug suppliers’ activities.
The unit of analysis in the assessment of supply control
is the market, typically in a city, region, or country.
Randomised controlled trials are sometimes possible at
the level of neighbourhood markets, but become
increasingly impractical for national or regional markets.
Most of what is known about supply control comes from
natural experiments, case studies, and economic analyses
that test theories developed in other contexts, thus
limiting the strength of evidence available on the
eff ectiveness of supply-side interventions (table 2).
Ideally, eff ective supply control would make a drug so
scarce that users could not fi nd suppliers without great
diffi culty or expense. The policy objective in the case of
non-users is to reduce exposure to drug sellers, which can
be achieved in some circumstances. For most of the 20th
century, heroin was largely absent from smaller towns
and rural areas in the USA and for whole countries
elsewhere in the world. Even at present, cocaine is not
readily available in many parts of Asia.
Drug markets are more diffi cult to suppress when they
become established. Drug prices can be kept high (when
price takes account of purity as well as volume). Product
illegality and law enforcement, even at low levels, increase
costs. For example, the illegal shipment of a kilogram of
cocaine from Colombia to the USA or Europe costs
US$10 000–15 000, whereas a package delivery service
can deliver a kilogram of a legal product for $50.2
Law enforcement also creates risks for sellers directly
(arrest and incarceration) and indirectly (eg, being
defrauded without legal recourse for compensation).
Drug market operators, therefore, receive far greater
Targeted policy Broad policy goals
Supply controlArrest traffi ckers and dealers; force suppliers to operate in
ineffi cient ways
Apply penalties for drug possession and use
Keep prices high; reduce availability
Identify problem drug users and divert into treatment
Deter drug use; prevent normalisation and spread
of drug use
Success at identifi cation and diversion
(overlap with evidence in treatment section)
Allow drugs for approved purposes; prevent use for
Improve health knowledge, change attitudes, and
prevent drug use
Stabilise and improve health, reduce overdose
deaths, prevent spread of HIV and other infections;
also reduce crime
Controls on prescription drugs Regulate pharmaceutical companies; restrict pharmacists and
physicians to approved treatments
Drug prevention programmes in schools and mass media
Attract problem drug users into treatment; enable them to
reduce and quit their drug use; and facilitate their recovery
Health and social services for drug users
Table 1: Methods and intended eff ects of drug policy approaches
Search strategy and selection criteria
We used several search strategies with special attention to
publicly available reviews of interventions for which suffi cient
well designed studies have been done to allow rigorous reviews
such as by the Cochrane Collaboration or by the National
Institute for Health and Clinical Excellence (NICE). We included
reviews done for the 2010 report Drug Policy and the Public
Good,2 which used an internal peer-review process to assess the
relevance of the work to public policy, and to gauge the
scientifi c strength of the evidence, supplemented by repeat
search in June, 2010, of literature databases Medline, PsycINFO,
and BioMed Central, as well as specialist databases including
the US National Institute of Drug Abuse and England’s National
Treatment Agency, Drug and Alcohol Findings, and DrugScope,
for additional randomised trials. We searched for studies in
English; studies in other languages were considered only if
identifi ed in our search or if authors were previously aware of
them. We used search terms including “prevention”, “schools”,
“policy”, “courts”, “prison”, “detoxifi cation”, “maintenance”,
“methadone”, “buprenorphine”, “naltrexone”, and
“prescription”. We also requested relevant material from key
experts and organisations. Peer-reviewed articles were initially
assessed by their titles and abstracts—we reviewed in full all
peer-reviewed articles identifi ed as potentially relevant.
www.thelancet.com Vol 379 January 7, 2012 73
monetary compensation than do people engaging in legal
markets.3 The distribution system passes these costs on
to users via higher drug prices.
Empirical evidence supports fi ve broad conclusions
about the eff ectiveness of supply control in keeping prices
high. First, if law enforcement can keep prices high, drug
initiation and use will be reduced. Many empirical studies
show that indicators of problem drug use, such as records
from emergency departments and arrestees’ urinalysis
results, respond to changes in purity-adjusted prices.4
Second, illegality and some basic level of enforcement
makes illicit drugs far more expensive at retail in
developed countries than plausible estimates of the cost
of their production and distribution would suggest.
Cocaine and heroin are semi-refi ned agricultural products
that retail for many times their weight in gold—their
legal, untaxed price would be like that of coff ee.5
Third, modelling studies, such as those pioneered
at RAND,6 have consistently shown that increasing
imprisonment is a very expensive way to increase prices
in established drug markets—fi ndings from empirical
studies are generally not encouraging about the potential
success of such control methods. For example, Kuziemko
and Levitt7 estimate that an increase in the number of
prisoners detained on drug-related off ences in the USA
from 82 000 to 376 000 between 1985 and 1996 increased
retail cocaine prices by only 5–15%. Fourth, very little
evidence exists for the eff ectiveness of alternative
development programmes in source countries, and no
evidence exists that they aff ect the availability or price of
Eff ectiveness Amount of research support
and cross-national testing
Alternative development in
No documented correlation with
reduced drug use in a fi nal-market
Typically no recordable eff ect on
downstream markets, but has
sometimes created a temporary
Good evidence for temporary
disruption in drug market
Programmes in most major
source countries have been
Eradication or bans in Mexico,
Turkey, and Afghanistan
coincident with reductions in
Several studies in the USA and
Alternative development takes time to reduce
production, allowing other regions to increase
production. Cost is very high
Production often shifts to other growing regions.
Costs include alienation of farmers whose crops are
Controls on precursor chemicals Cheap to initiate through legal statutes but
enforcement can be costly. New production
materials then used or producers move to other
Drug price increases compared with equivalent
legal-market prices, suggesting important benefi ts
of small investments but little evidence of a
dose-response eff ect. Interdiction programmes are
costly to implement but some aspects have
effi ciences with other border control eff orts
Incarcerating high-level dealers can be more
cost-eff ective than enforcement against retail
sellers because retail sellers can easily be replaced,
but no head-to-head empirical tests of relative
cost-eff ectiveness exist
Conventional approaches can be very costly to
implement and sustain. However, case studies are
available of more modern approaches that yield
success with far fewer arrests and incarcerations
Expensive to manage prison system and
community re-engagement services
InterdictionCan disrupt drug market and
supply chain, and thus keep retail
price of drugs up
Several studies involving the
USA and cocaine-producing
and transhipment countries
High-level enforcement through
Price mark-ups suggest important
benefi ts of small investments but
little evidence of a dose-response
Only a few studies have been
Street-level enforcement Stronger evidence of ability to
suppress fl agrant use of drugs and
market-related harms than to
reduce drug use
Some evidence but diminishing
returns from imprisonment
beyond specifi c levels
Small or no eff ect on cannabis
use, although reduces adverse
consequences for users
Moderate or no eff ects on
Only a few studies done
outside the USA
Only a few investigations
done outside the USA or
Several Australian and US
Non-criminal penalties imposed
for cannabis use and possession
Some benefi ts to criminal justice system with
contested eff ect on cannabis use and related
Some benefi ts to criminal justice system
Reduction of the level of criminal
penalties (mainly for cannabis use
Diversion to mandated education
Legalisation (to all intents and
purposes) of a controlled retail
Contested evidence from the
USA, the Netherlands, and
Several Portuguese and US
Several assessment studies in
the Netherlands, but no
Little eff ect on cannabis-related
Circumstantial evidence that the
Dutch system might be eff ective
in the separation of cannabis
from other drug markets
Diversion saved money in California, USA
Eff ects on cannabis consumption are contested but
Dutch use rates are low compared with other
No interventions in this table have been subject to randomised assessments—such assessments are unlikely to be done. Studies of changes in criminal penalties have focused
largely on cannabis. Adapted from reference 2.
Table 2: Evidence for supply control and criminal justice interventions
www.thelancet.com Vol 379 January 7, 2012
drugs in fi nal-market countries (although they can
possibly trigger a shift in location of production).2
Fifth, supply shocks can substantially reduce drug
availability, purity, use, and harms in consumer
countries—eg, metamfetamine precursor controls,8 the
Taliban opium ban,9 the 1989–90 war on Colombian drug
traffi ckers,10 and the Australian heroin shortage.11 These
successes often stem from a convergence of fortuitous
circumstances that governments can rarely reproduce by
design. Occasionally they follow deliberate actions such
as introduction of legislation to regulate precursor
chemicals involved in illicit drug preparation,12 although
results are not always predictable or simply generalisable.13
However, their success lasts for only as long as it takes
the market to adapt. Many attempts to disrupt supply
produce no detectable eff ects.14 Their eff ects on drug
users can sometimes be adverse15 and sometimes
benefi cial;16 the diff erence is probably related to age,
regularity, and disadvantage of the users.11,16 The cost-
eff ectiveness of these eff orts is not easily assessed.
Distinct from reducing supply, law enforcement can
seek to manage the collateral harms from illicit markets,
such as drug-selling and violence on street-corners.
When police target high-visibility dealing, markets often
re-emerge in a diff erent place or form. Such diffi culties
limit the eff ect of law enforcement on drug use but can
reduce market-related harms.17 Drugs can be distributed
by violent gangs that corrupt offi cials, terrorise neigh-
bours, and employ children as look-outs. They can also
be distributed surreptitiously, behind closed doors
through social networks. A policy that discourages more
socially harmful dealing practices can reduce harm and
improve community amenity. This approach has been
used to reduce fl agrant selling of illicit drugs (eg, in High
Point, NC, USA)18 and drug-related violence (eg, in
Boston, MA, USA).19
A second additional function of law enforcement is to
enforce laws against drug users. Enormous variation
exists in how harshly countries apply these laws and to
which substances. Some countries have reputations
for toughness (Singapore, Saudi Arabia, or China
immediately after the 1949 revolution), whereas, in many
countries, users are rarely imprisoned for drug use, even
when such sentences are allowed in law.
The distinction between drug use and involvement in
drug-selling or distribution is often unclear. In the USA,
more than 90% of people imprisoned for drug-law
violations admit playing some—perhaps minor—part in
drug distribution.20 And the law enforcement response
also varies greatly, with other sanctions used that do
not include imprisonment—namely, arrest, fi nes, com-
munity service, brief incarcerations, and loss of
benefi ts—eg, eligibility for school athletic programmes
or public housing.
Drug users’ risks of arrest and the consequences of
arrest vary substantially between countries. Research on
the eff ect of these variations is sparse and of poor quality.
Most studies have been of the eff ects of cannabis
decriminalisation,21 but are methodologically weak, often
involving comparisons of prevalence before and after law
changes that treat decriminalisation as a binary variable.22
Interpretations of the evidence are contested, but, evidence
that tougher sanctions deter drug use or criminal
off ending more generally is, at best, weak.23
By contrast, increasing evidence shows that specifi c,
immediate, and brief sentences (eg, overnight) for positive
drug tests produce substantial reductions in drug use and
off ending in individuals who are under criminal justice
supervision.24 The typical setting for such coerced or
mandated abstinence is in off enders on community
release (before trial, on probation, or on parole). They are
drug tested at least once a week (sometimes once a day or
even twice a day), with the typical sanction for a missed or
drug-positive test being 24 h in jail.25 Evidence for such
mandated abstinence programmes comes from drug and
drink-driving off enders on community release25,26 and
programmes for addicted physicians and airline pilots.27
A fourth function of law enforcement is to encourage
drug users to enter and remain in treatment. Drug courts
are one approach that can be more eff ective than suspended
sentences or other diversion programmes in keeping clients
in treatment.28 However, the scale-up of this approach to
community levels has been diffi cult. Many academics are
sceptical about the ability of law enforcement to suppress
drug use in established drug markets through supply
control or user sanctions. Available evidence is more
positive, however, about enforcement’s capacity to reduce
adverse collateral eff ects of drug markets, produce
abstinence in closely supervised off enders, and improve
uptake and retention in treatment (as seen without judicial
intervention). See webappendix for further reading.
Prescription regimens to control pharmaceutical
Many illicit drugs were originally created for medical use29
and many are still used as such (eg, opioids). Prescription
regimens are a widely used form of drug control in
developed countries in which a physician prescribes a
drug that is dispensed by a pharmacist. Such regimens
are the outcomes of incremental policies fi rst introduced
about a century ago. Natural experiments provide useful
lessons on the eff ectiveness of diff erent prescription
regimens in the control of psychoactive drugs (table 3).
In the past decade, misuse of sustained and slow-
release prescrip tion opioid analgesics (eg, oxycodone,
hydrocodone, oral morphine) in the USA and Canada
has increased. This change has been accompanied by
increased morbidity (eg, emergency room and drug
treatment admissions) and mortality (eg, accidental
poisonings) since the early 1990s.30–32
Prescription regimens do not eliminate non-medical
use of psychoactive prescription drugs. Sourcing of
prescription drugs occurs through diff erent forms of
diversion—eg, double doctoring, prescription drug
See Online for webappendix
www.thelancet.com Vol 379 January 7, 2012 75
fraud, and thefts and robberies.33,34 Family and friends
are also a primary source for individuals who use
pharmaceuticals non-medically. Such sourcing patterns
make the reduction of supply through traditional law
enforcement diffi cult. The emergence of internet-based
pharmacy services makes control even more diffi cult.35,36
The high availability and diversion of prescription opioid
drugs in North America has led to the prescription of
opioid analgesics to replace heroin in many injecting
Prescription monitoring systems can reduce irregu lar
prescribing practices, but a balance is needed (eg,
between the need for access to drugs for legitimate pain
relief and the need to restrict access to deter inappropriate
non-medicinal use). The introduction of a prescription-
monitoring system for barbiturates (1981) and benzo-
diazepines (1989) in New York State, USA, greatly
reduced excessive prescription of these drugs.39,40 In the
UK in the 1970s, barbiturate prescription was reduced by
more restrictive professional guidance (the Campaign
on the Use and Restriction of Barbiturates initiative).
Later, professional guidance to restrict long-term pre-
scription of benzo diazepines led to substantial reduction
in overall prescribing.
Monitoring and supervision are usually incorporated
as integral elements of the provision of opioid substitution
therapies (OSTs), with contingent relaxation of super-
vision requirements. An increased involvement of
prescribed methadone in overdose deaths was recorded
in the UK41 that was postulated to be caused by
unsupervised methadone consumption. Supervised
consumption was subsequently widely introduced42 and
the involvement of methadone in overdose deaths
reduced substantially thereafter.43
Two caveats of this approach should be noted. First,
reduced prescription of some drugs can be followed by
increased use of other prescription drugs with similar
eff ects. Second, any eff ort in this area has the potential to
deny needed medications to ill individuals, and this
concern should be balanced against concerns about abuse
and diversion. See webappendix for further reading.
Young people are an obvious and important focus for
prevention because the period between being a child and
being a young adult is when most people are initially
exposed to drugs, and when they are most likely to initiate
use. Ideally, preventive interventions should stop young
people from starting drug use, but they can also delay
initiation of drug use and prevent young people from
becoming regular and dependent drug users.
Prevention programmes are often categorised by venue
(school, media, community, primary health care, etc), but
other categories exist: environmental interventions that
limit the availability of dangerous substances, psychosocial
developmental interventions, educational interventions
Eff ectiveness Amount of research support
and cross-national testing
Change cost or reimbursement Some evidence for an eff ect on
Most studies are from Canada.
Single studies in Australia,
Germany, Norway, Sweden, and
Three studies from Canada and
Some evidence for analgesics when alternative
drugs are available
Restrict OTC sales Confl icting results from studies of
No studies of psychoactive substances. Some
evidence that OTC restrictions prevent analgesic
Changing a drug between OTC and prescription
states has varying eff ects on sales. In some
systems, the consumer pays more for an OTC
Some evidence that advice to physicians
changes prescribing behaviour, but no studies of
Although prescription of targeted drugs is
reduced, there is risk of substitution of drugs
that are equally or even more harmful
Make available only with
prescription (vs OTC availability)
Sparse research lends support to
some eff ect
Studies in Sweden, the UK, and
the USA of non-psychoactive
substances; one study in Chile of
a psychoactive substance
Six studies from Australia
Canada, the UK, and the USA
Authoritative advice to physicians
on adverse eff ects
Some evidence of eff ects when
another drug is available
Prescription restrictions, registers,
Good evidence that registers and
monitoring reduces prescription of
targeted drugs and reduces
Very little published research
Many studies from various
European and North American
Restrict list of prescribersIndividual studies in Iran and
the UK identifi ed positive
Studies from various European
countries, Australia, and the
Studies in Australia, Denmark,
the UK, and the USA
In need of further replication studies
Withdraw prescription availability Good evidence for the reduction of
prescribing and use of the drug
Replacement drugs can carry additional risks
Controls on administering OST Some eff ects in the reduction of
overdoses from supervised OST
Some evidence for reduced diversion
OST=opioid substitution therapy. OTC=over-the-counter. Adapted from reference 2.
Table 3: Evidence for prescription regimens
www.thelancet.com Vol 379 January 7, 2012
that aim to raise awareness and knowledge of the adverse
eff ects of drugs, and screening and brief intervention
programmes in health settings. Psycho social developmental
and educational interventions—approaches aimed at
reducing demand—have been a mainstay of national drug
prevention policies in many countries for many years.
Although evidence is strongest in the context of school-
based programmes, Cochrane systematic reviews of
randomised controlled assess ments44,45 and other high
quality reviews show that psychosocial developmental
interventions can be eff ect ive, whereas knowledge and
awareness are generally ineff ective for prevention of use of
illicit drugs,44,46 tobacco, and alcohol (table 4).
The ineff ectiveness of didactic educational tactics is a
serious challenge for mass media approaches and also
many traditional community and classroom pro-
grammes. For example, Drug Abuse Resistance
Education (DARE) is a school-based preventive inter-
vention widely adopted in the USA in which police
offi cers provide classroom advice on the dangers of drug
use. In many studies it has been shown to neither
prevent nor delay drug use.47 Likewise a large-scale
assessment of a mass media campaign to prevent
cannabis use also showed that it had, at best, no eff ect,
and possibly increased use.
Not all psychosocial interventions fare well in assess-
ments, but fi ndings from a few high quality studies
indicate that some family-based and classroom inter-
ventions can reduce drug or alcohol use. These
interventions do not focus exclusively or specifi cally on
drug or alcohol use; they aim to develop pro-social
behaviour and social skills more generally, and they have
benefi ts beyond the reduction of drug or alcohol misuse,
such as the reduction of violence and mental health
problems. Three interventions aimed at drug-use pre-
vention for which supportive research evidence exists are
the Strengthening Families Programme for young people
aged 10–14 years and their parents (SFP10-14), social or life
skills training, and the Good Behaviour Game.2 The Good
Behaviour Game, a classroom behaviour manage ment
approach delivered in some primary and elementary
schools in the USA and some countries in Europe when
children are aged 5–7 years, has reported positive outcomes
15 years after intervention, when young people were aged
20–21 years.48 There are also tactics, such as correcting
young people’s misperceptions about how common drug
use is, that have been shown to be eff ective.
Beyond primary prevention,49 research from several
countries (Australia, Brazil, India, and the USA) has
examined the secondary prevention of substance
misuse, based on screening and brief intervention in
primary care and other settings. Brief intervention in a
clinical setting can reduce cocaine and heroin use, even
without meaningful contact with the treatment system.49
Eff ectiveness Amount of research support
and cross-national testing
Family or parenting programmes Some studies show eff ectiveness
in the reduction of the onset of
A few studies done in the
Positive fi ndings for the universal Strengthening
Families Programme for people aged 10–14 years and
their parents with longer-term follow-up and
cost-eff ectiveness analysis. Replication needed.
Assessments of other family or parenting
programmes have not been as positive
In one study, the Good Behaviour Game reduced
lifetime drug misuse by up to 50% in boys 14 years
after the programme, with stronger eff ects with boys
identifi ed when aged 6 years as highly aggressive and
disruptive. One US study did not replicate this
outcome; Dutch and Belgian studies show promising
short-term eff ects
A few assessments have shown positive intervention
eff ects from a small set of prevention programmes for
cannabis use and the use of other drugs
Environmental or classroom
Some evidence in support of the
Good Behaviour Game
A few studies done in the
USA, the Netherlands, and
Social or life skillsShort-term eff ectiveness is
equivocal. Some evidence of
positive eff ect in the medium to
No evidence of eff ectiveness
Several high-quality studies
done in the USA only
Multi-component community Only a few small USA studies Studies have typically combined school and
non-school approaches. Eff ect sizes tend to be
small or negligible
Few well controlled studies—but many uncontrolled
assessments—have been done
Few high-quality scientifi c assessments
Information about adverse drug
eff ects only
No evidence of eff ectivenessA few school-based studies
done in the USA
Research restricted to a few
studies in the USA
Several well controlled
studies and many
No evidence of eff ectiveness
Drug Abuse Resistance Education
No evidence of eff ectiveness
Despite DARE’s widespread use, meta-analyses show
that the programme is ineff ective
Adapted from reference 2.
Table 4: Evidence for prevention programmes targeting non-users of drugs, casual users, parents, and the general public
www.thelancet.com Vol 379 January 7, 2012 77
One session of motivational interviewing with drug-
taking college students led to pronounced reductions in
their use of cannabis, alcohol, and tobacco.50 Provision
of a self-help booklet and one session of motivational
interviewing reduced amphet amine consumption in
regular users.51 Two studies52,53 noted that general
practitioners can reduce excessive benzodiazepine use
in their patients with brief interventions such as letters
or consultations. In a large cross-national trial of brief
intervention with drug users, Humeniuk and coleagues54
recorded substantial reduc tions in illicit drug use after
one brief intervention in primary care settings. With
school-age adolescents, screening and personality-
targeted coping skills greatly reduced initiation and the
frequency of drug use.55 However, benefi ts might
deteriorate over time56 and other investigators have
reported negative fi ndings.57 Findings from attempts to
implement these interventions on a wider scale have
Each society needs to make a political judgment about
whether the small to medium-sized eff ects of psychosocial
developmental interventions are worth the cost of
delivering them.61 Economic analyses suggest that these
interventions are cost-eff ective because the lifetime
benefi ts of even slightly lower rates of early drug or alcohol
use are substantial. See webappendix for further reading.
Health and social services for drug users
This section covers all interventions designed to change
the behaviour of drug users for their benefi t and the
benefi t of others aff ected by their drug use—ie, family
members, neighbours, and colleagues. It includes
addiction treatments that enable and support abstinence,
health services that aim to reduce the amount and
frequency of drug use and the harms arising from it, and
interventions to change behaviours that are harmful to the
individual and society—eg, behaviours that increase risks
of HIV infection, drug overdose, and drug-related crime.
How these interventions are organised and delivered is
important. No matter how effi cacious a treatment might
be, it will produce little benefi t to individuals and society
if it is inaccessible, or if it is provided in a way that
discourages help-seeking behaviour or reduces retention
in care. Much better results are achieved by well organised
programmes with more comprehensive services.62,63 The
diff erence in benefi ts between the best and worst pro-
grammes can be very large but the reasons for these
diff erences are unclear.
“Treatment works” is an often-quoted mantra intended
to alert health professionals and the public to the benefi ts
of addiction treatment. But this is not true of all types of
intervention for all problem drug users. The treatment
with the strongest evidence of effi cacy is substitution
treatment for addiction to heroin and other opioids
(table 5). Evidence is much weaker for treatment
of problem use of other drugs (such as cocaine,
crack cocaine, methamfetamine). Some non-pharma-
cological approaches described below have effi cacy across
diff erent forms of substance abuse.
OSTs are the most extensively studied and controversial
forms of treatment.63–65 They consist of the regular
provision of a prescribed replacement supply of opioid
drug, usually in longer-acting oral form to avoid swings
between intoxication and withdrawal. They are usually
taken under direct supervision (especially during the
early stages of treatment).
These forms of treatment can enable a person to
establish a healthier lifestyle, which, for some individuals,
is the main benefi t of treatment—for others, having a
healthier lifestyle can lead to sustained abstinence from
use of illicit drugs. OST has mostly been studied with
oral methadone or sublingual buprenorphine,64 although
other drugs have been used with benefi t, but with a
smaller evidence base.66–69 Attrition and relapse are major
challenges.64,65 Retention in OST is generally better with
methadone than it is with buprenorphine,64,65 whereas
drug-free urine (indicating quitting heroin) is generally
better with buprenorphine.64,65 An adaption during the
past decade has been a buprenorphine and naloxone
combination tablet, which has been developed to reduce
potential for intravenous misuse—the extent of extra
benefi t has not yet been established. These substitution
approaches have repeatedly been shown in studies in
many countries to produce a wide range of benefi ts in
the reduction of heroin use, overdose mortality, HIV
transmission, and crime.64,70–72 The greatest benefi ts are
seen when treatment is optimised with adequate drug
doses and ancillary treatments and support,62–64,70,72
although some benefi t is seen even with low dose and
Several other types of medication are available, but do
not have the same strength of evidence as OST. Naltrexone
(oral) is a highly effi cient opioid antagonist that can support
abstinence and prevent relapse in the event of further
instances of heroin use. However, its use is rare because
adherence is often poor,73,74 even though better results can
be achieved when given under supervision or with
behavioural reinforcement.73 Both implantable and
injectable sustained-release versions of naltrexone have
been developed to circumvent this adherence problem,
with positive initial results.
Sustained-release versions of OST have been explored,
including long-acting oral levo-alpha-acetylmethadol
(subsequently withdrawn after concern about QT pro-
longation), high-dose sublingual buprenorphine to
enable dosing three times a week, and pilot formulations
of long-acting depot injection and ultra-long-acting
implant of buprenorphine (see webappendix for
references on sustained release OST).
A supervised injectable treatment with maintenance
doses of supervised diamorphine (pharmaceutical
heroin) has been studied in randomised trials in several
countries, for the treatment of refractory chronic heroin
addicts, with positive fi ndings.68,69
www.thelancet.com Vol 379 January 7, 2012
The provision of emergency naloxone (injection) to
prevent heroin overdose death (while waiting for an
ambulance) has been introduced in some countries,
including the training of users75 and families in emergency
resuscitation,76 but evidence is thus far observational. The
prescribing of stimulant substitution treatment for
cocaine and amphetamine addiction has been piloted,77
but retention has been very poor and reliable evidence of
its benefi t is scarce. Vaccination against the specifi c drug
has become technically feasible and is being tested against
cocaine, but with unclear results thus far.78
Behavioural and psychosocial interventions, unlike
OST, are not confi ned to problem users of any particular
drug, and include therapeutic communities, contingency
management, and brief interventions. Observational
evidence shows the eff ectiveness of residential rehabili-
tation, with either a 12-step or therapeutic community
orientation.79–81 However, few randomised trials have been
done.82 Longer retention in treatment is associated with
better outcome but the direction of causality is unclear.
No clear evidence exists from randomised trials of a
benefi t from longer duration of programmme83 or from
residential versus day care,84 although a large prospective
observational study recorded slightly greater benefi t from
12-step versus relapse-prevention cognitive behavioural
treatment or eclectic approaches.85
Eff ectiveness Amount of research support
and cross-national testing
Methadone or buprenorphine
opioid substitution treatment
Good evidence for reduced
mortality, heroin use, other drug
use, crime, HIV infection, and
Studies done in many countries,
including Australia, China, France,
Germany, Indonesia, Italy, Iran,
Lithuania, Malaysia, Poland,
Spain, Sweden, Switzerland,
Thailand, Ukraine, UK, and USA
Appropriate for opiate users only. Combination
with psychosocial services enhances outcome.
Cost-eff ectiveness is high relative to other treatment
interventions. The evidence-base is slightly stronger
for methadone. The buprenorphine evidence-base
might change after release of a buprenorphine plus
naloxone combination formulation
In Austria, slow-release oral morphine OST is used as
well as methadone OST. It might have value for
patients for whom methadone OST is not benefi cial
Appropriate for opiate users only. Randomised trials
have consistently shown positive results with this
population, but heroin OST is the most expensive
form of OST and is usually reserved for dependent
users who have not responded to oral OST
Targeted at opiate users, less than 20% of whom are
willing to try this treatment. Oral naltrexone studies
are of poor methodological quality and do not lend
support to the potential eff ectiveness of the
Targeted at injecting drug users. Might prevent
HIV infections but have no evidence of reducing
Hepatitis C infections. NEPs have never been assessed
by a randomised clinical trial
Appropriate for individuals using a range of drugs and
administration routes. Can be combined with
pharmaceutical treatment and delivered in outpatient
and residential settings in group or individual formats
Not widely applied in the USA, not tested in other
Slow-release oral morphine
Few studies, but produces similar
benefi t to methadone OST
Trial data mostly from Austria,
plus exploratory studies from
and randomised clinical trials in
Switzerland, the Netherlands,
Germany, Canada, and the UK
Evidence of eff ectiveness in
reducing or stopping use of
street heroin in individuals who
do not respond to oral OST
Oral opiate antagonists
(eg, naltrexone) maintenance
Some evidence for reduced
opiate use but compliance to
treatment is a major limitation
Few studies outside of the USA
Needle exchange programme
Observational evidence that
NEPs can reduce HIV infections
and enable treatment
Good evidence for reducing drug
use, drug-related problems, and
Most research done in Canada,
the UK, Australia, and the USA
Studies in most high-income
countries and many low-income
and middle-income countries,
including India, Mexico, and Peru
Research evidence is mostly from
Behavioural family-based and
Several randomised trials show
improved retention and benefi t
during treatment for heroin or
Very few randomised trials.
Longer duration of residence
associated with better outcome,
although randomised trials show
equal benefi t from shorter
programmes with follow-up or
with similar day care
Good evidence for the reduction
of drug use and crime
Only moderate quantity of
good-quality research evidence,
despite long history of provision
Extensively provided around the world in diff erent
forms, some based on programmatic therapeutic
communities, some based on 12-step rehabilitation
and recovery, and some based around religious
Peer self-help organisations Evidence available from a range
of countries as diverse as the USA,
the UK, Iran, and China
Evidence available from the UK,
the USA, South Africa, India,
Australia, and Brazil
Highly cost eff ective. Probably the most widely
available method of treatment globally
Brief interventions in general
Good evidence for reducing drug
use by at-risk drug users
Evidence available for a variety of substances
Adapted from reference 2.
Table 5: Evidence for health and social services for established drug users
www.thelancet.com Vol 379 January 7, 2012 79
Contingency management (eg, the use of voucher
reinforcement for drug-free urine samples)70,86–88 has been
shown in many randomised trials (which used specially-
trained research therapists and rewards of small monetary
value) to substantially increase abstin ence,70,86,87 atten-
dance,86,87 and attention to associated health needs.89,90
Some of these behavioural approaches can be used
eff ectively in combination with drugs to improve adher-
ence and treatment benefi ts.49,60
In addition to contingency management, several
specifi c forms of psychological intervention have been
identifi ed in a review by the UK’s National Institute for
Health and Clinical Excellence (NICE) as having a robust
evidence base.70 Opportunistic brief interventions for
drug users with very low or no contact with treatment
can increase help-seeking behaviour and stimulate
change in drug use behaviour.50,91,92 Brief motivational
techniques applied in primary care or at needle and
syringe exchange schemes can aff ect drug use.93
Behavioural family-based and couples-based inter-
ventions in the treatment of heroin or cocaine addiction,
usually integrated with drug treatments, produce better
abstinence rates both during treatment and at follow-up,
and also lessen drug use if it persists.94,95 Synergistic
benefi ts are also seen with active referral to 12-step
groups from within treatment programmes with better
sustained attendance at self-help groups after intensive
referral.96 Cognitive behavioural treatment is of benefi t
for associated comorbidities, but evidence of a specifi c
benefi t in the treatment of drug dependence is unclear.70
Needle and syringe programmes provide injecting
drug users with sterile needles and syringes, often in
exchange for used equipment. These interventions
reduce sharing of needles and syringes and infectious
disease transmission rather than drug use itself. In some
cases, they provide a gateway for drug users to enter
addiction treatment and ultimately, cease drug use.97
Needle and syringe programmes can be incorporated
into existing drug treatment services or provided through
Such programmes have never been the subject of a
controlled clinical trial. Nonetheless, fi ndings from a
review show strong evidence that syringe exchange
programmes reduce injection risk behaviour and
suggest that they also reduce HIV transmission.98 The
amount of risk behaviour change induced by needle and
syringe programmes does not seem suffi cient to protect
against hepatitis C, which is much more easily
transmitted than HIV.99
Peer-led mutual health organisations (such as Narcotics
Anonymous, Cocaine Anonymous, and Women for
Sobriety) are led by people who are recovering from
addiction (Narcotics Anonymous and Cocaine Anonymous
are also examples of 12-step programmes). Although self-
help is probably the most common type of intervention
delivered globally for problem drug use, there were until
the past two decades very few scientifi c studies of its
eff ectiveness. As with studies of alcohol,100 evidence now
shows that that participation in Narcotics Anonymous is
associated with continued abstinence, lower health-care
costs, and improvement in other areas of functioning.101–103
Drug policy to promote the public good
Scientifi c research can make important contributions
to the construction of more eff ective drug policy, but
fi nal resource allocation involves wider public and
political processes of priority-setting.104 At least three
types of benefi t can be identifi ed: a substantial benefi t
to individuals from major changes (eg, OST), widely
dispersed benefi ts from interventions with a small
eff ect on individuals (eg, screening and brief inter-
vention) but substantial population benefi t, and indirect
benefi ts to others (eg, reduced HIV transmission and
reduced crime from OST).
A conceptual framework is described in the fi gure, to
inform debate and organise the major public policy
options. The fi gure presents a four-tier pyramid that
describes potential for the maximisation of the public
good as well as individual benefi t and can constructively
inform the political and economic considerations of
diff erent policy initiatives. This model is informed by
similar frameworks in tobacco control, communicable
disease control, and injury prevention.105
The bottom tier of the pyramid represents the
traditional population-wide (universal) interventions that
aim to limit drug supply through interdiction, precursor
controls, prescription regimens, and related measures.
Although the evidence is mixed, and the quality of the
research is poor, supply control can have a substantial
population eff ect, if eff ective methods are used (as is the
case with tobacco and alcohol). The success of such
control in the drugs fi eld has been shown in the control
of prescription drug epidemics106,107 and the elimination
of metamfetamine laboratories.108
Interventions at the top tiers provide direct help to
drug-aff ected individuals. Individuals (and their carers)
typically need to expend much personal eff ort to receive
Figure: The eff ect of drug policy options on the public good and individuals
for drug users
www.thelancet.com Vol 379 January 7, 2012
benefi t from these interventions, which can adversely
aff ect adherence. Secondary prevention approaches for
problem drug users can prevent deterioration and linked
adverse events (eg, HIV, crime) and are included in the
second tier because the most eff ective of these can reach
many severely problematic drug users in the commun-
ity at a time when they are readily accessible. The
population-level eff ect of such services (in the top two
tiers) can be further enhanced by increasing availability
within the criminal justice system and by use of the
leverage of that system to reward behaviour change.
Treatment in this setting can be as eff ective as that in
the community when supported by the courts with, for
example, diversion into treatment and regular drug
testing as an alternative to incarceration.
The second and third tiers represent diff erent types of
prevention. These can be either universal—whole popu-
lation or community eff orts—or more selective and
indicated forms of secondary prevention targeted at high-
risk groups. Although only preliminary evidence exists,
screening, brief advice and counselling can potentially
reach many at-risk individuals, and aid referral to treat-
ment for those individuals with the most severe drug
problems. Some universal prevention programmes—
those aimed at the prevention or delay of use of drugs by
young people—have evidence of eff ectiveness, albeit with
a small to medium-sized eff ect. The eff ective early
intervention prevention programmes concentrate on the
psychosocial development of young people and also have
benefi ts beyond the prevention of drug misuse.
Between countries and over time, the actual health
needs and the extent of public commitment to the
provision of interventions will diff er. For a society faced
with the active spread of HIV through injecting drug use,
the priorities will be diff erent from those of a country
tackling the continuing addiction problems from a heroin
epidemic a decade before.
The interventions themselves vary greatly in relevance.
Investments in the strengthening of border security have
no relevance to drug problems that involve domestically
produced or legal products (such as solvent misuse by
adolescents or the misuse of legal pharmaceutical opioids
in the USA). The evidence of benefi t from OSTs is of little
value to a society mainly affl icted by a cocaine or
amphetamine problem, as is the situation for most of
South and Central America. Similarly, the benefi ts of
needle and syringe programmes will depend on the extent
of injecting drug use, sharing of needles, and prevalence
of HIV. They are much less relevant to societies where
injecting is uncommon, such as those where opioid
addiction involves swallowing, smoking, or inhaling the
drug (as was previously the case for much of central and
southeast Asia). However, the pyramid of policy options
outlined above is useful in the identifi cation of
interventions, even though the specifi c problems and the
most appropriate type of interventions will vary over time
and between societies and geographical locations.
Drug policy has the potential to contribute more to the
public good by focusing on interventions with the largest
potential population eff ect, the strongest evidence of
eff ectiveness and cost-eff ectiveness, and the closest link
between the outcomes of the policy and society’s idea of
the public good. Funders and researchers should pay
greater attention to more policy-relevant areas in addiction
research study if society’s ability to adopt a more evidence-
based approach to drug policy is to be improved.
By a shift in focus to maximisation of the public good,
greater societal and political support can be generated
for evidence-based measures that avoid the detrimental
eff ects of the marginalisation of drug users by, among
other strategies, the imposing of severe criminal
penalties. Diff erent interventions might be more
eff ective or feasible for diff erent drug problems. A
comprehensive public policy approach would implement
evidence-based measures at each level of intervention
and maximise the synergy between these levels—
for example, through collaboration and coordination
between the criminal justice system and treatment
providers, which has already been shown in some
countries (eg, the USA) to produce synergy between
supply control eff orts and the health service system.
Long-term benefi ts of these policies would thus increase
for whole communities as well as for individuals.
All authors contributed to the data collection for and writing of this
paper, each leading the writing for areas in which they have expertise.
Confl icts of interest
JS declares that he has worked with UK and international government
agencies on treatment guidelines, including chairing UK Department of
Health and NICE clinical guidelines committees; has contributed to the
work of organisations that review evidence of eff ectiveness of drug
policy; has received research and educational grant support or honoraria,
consultancy payments, and travelling, accommodation, or conference
expenses from pharmaceutical companies who produce, or have been
considering producing, new medicines or new formulations for use in
the addiction treatment fi eld, including (past 3 years) Genus (Britannia),
Viropharma (Auralis), Martindale (Catalent), Reckitt-Benckiser,
Schering-Plough, Lundbeck, UCB, Napp (MundiPharma), Lightlake, and
Fidelity International; works within an integrated university and NHS
academic health sciences centre (Kings Health Partners AHSC) and is
supported by the NIHR Biomedical Research Centre for Mental Health
at the Institute of Psychiatry, Kings College London and South London
and Maudsley NHS Foundation Trust that provides treatments and
undertakes research study; and has close links with various other
treatment provider organisations. DF’s Department has received
funding from the alcohol industry for alcohol education and prevention
materials that are being assessed in a randomised controlled trial funded
by the Medical Research Council and led by Cardiff University. DF is a
Trustee of the UK alcohol education charity, the Drinkaware Trust.
BF has consulted for government and non-governmental organisations
at national and supranational levels with regard to drug policy and
related interventions; travel costs and activity honoraria were received for
some of these activities. All other authors declare that they have no
confl icts of interest.
Views expressed in this paper are the authors’ individual personal
judgments and are not the offi cial views of any government or other
organisation with which the authors have worked or been associated.
The paper uses information collected for the publication of a document
entitled Drug Policy and the Public Good,2 which was funded by the UK
www.thelancet.com Vol 379 January 7, 2012 81
Society for the Study of Addiction—all authors were involved with this
project. We thank John Witton for assistance with the search of
published studies. BF holds the CIHR/PHAC Chair In Applied Public
Health; KH holds an honorary professorship at King’s College London.
Tables 2–5 are adapted from the appendices of the book ‘Drug Policy and
the Public Good’ (reference 2). We also wish to thank our co-authors of
this book (Griffi th Edwards, Isidore Obot, Jurgen Rehm, Peter Reuter,
Robin Room, and Ingeborg Rossow) from whose structure and earlier
examination we have drawn on in the preparation of this paper.
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