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Australian and New Zealand Journal of Psychiatry
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Changes in use of psychostimulant medication for ADHD in South Australia
(1990-2006)
Brenton Prosser a; Robert Reid b
a Hawke Research Institute, University of South Australia, Mawson Lakes, SA, Australia b Department of
Special Education, University of Nebraska, Barkley Center, Lincoln, Nebraska, USA
Online Publication Date: 01 April 2009
To cite this Article Prosser, Brenton and Reid, Robert(2009)'Changes in use of psychostimulant medication for ADHD in South
Australia (1990-2006)',Australian and New Zealand Journal of Psychiatry,43:4,340 — 347
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Changes in use of psychostimulant medication
for ADHD in South Australia (1990
2006)
Brenton Prosser, Robert Reid
Objective: The aim of the present study was to undertake a retrospective analysis of
archival data on psychostimulant prescriptions from South Australia for the periods 1990
2000 and 20012006 for 7849 youths aged from birth to 18 years.
Method: A person-based data set was used to assess: (i) rate of new prescriptions by age
group; (ii) demographic characteristics (age of psychostimulant start, male: female ratio);
(iii) duration of psychostimulant use; and (iv) geographic variation in psychostimulant
prescription.
Results: Four major findings were observed: (i) the rate of new prescriptions was highly
variable both for 19902000 and 20002006; (ii) demographic characteristics such as start
age and male:female ratio declined over both periods; (iii) the duration of psychostimulant
use was approximately 2.5 years for 19902000 and 2.0 years for 20002006; and (iv)
there was geographic variation in both periods with a significant correlation between
socioeconomic status and prescription rate per region.
Conclusions: The patterns of psychostimulant use in Australia closely parallel the USA.
Physicians’ prescribing practice may be extremely volatile. Duration of psychostimulant
treatment should receive increased attention. There is pronounced geographic variability in
prescription rates, which may be related to socioeconomic status.
Key words: attention-deficithyperactivity disorder, pharmacotherapy, psychostimulants,
socioeconomic status.
Australian and New Zealand Journal of Psychiatry 2009; 43:340
347
A central pillar of the recommended multi-modal
treatment approach for attention-deficithyperactiv-
ity disorder (ADHD) is psychostimulant medication
[1]. Around 75% of children who receive an ADHD
diagnosis will also receive psychostimulants [25].
The effectiveness of psychostimulants in the treat-
ment of ADHD has been demonstrated because they
can dramatically reduce ratings of symptom severity
[69]. The effectiveness of this treatment saw psy-
chostimulant use for ADHD increase significantly in
Western nations over the last two decades [10]. (The
authors note the controversy around psychostimulant
treatment for ADHD. There is continued debate
about the possible misdiagnosis or overdiagnosis of
ADHD and whether psychostimulant treatment is
warranted in the case of every young person diag-
nosed with ADHD. The data used for the present
study provided no information on diagnosis, only
that medication had been prescribed (a process that
legally requires diagnosis in this jurisdiction). Thus,
the matter of appropriateness of psychostimulant
treatment is beyond the scope of this paper. For
more detailed discussion of the issue of diagnostic
practices, we note the first author’s book [11].)
Due to the prominence of ADHD in the USA, this
nation provides a useful context against which to
Brenton Prosser, Research Fellow (Correspondence)
Hawke Research Institute, University of South Australia, Room G2-25,
Mawson Lakes Campus, Mawson Lakes,SA 5095,Australia.Email:
brenton.prosser@unisa.edu.au
Robert Reid, Professor
Department of Special Education, University of Nebraska, Barkley
Center,Lincoln,Nebraska,USA
Received 2 November 2008; accepted 19 November 2008.
#2009 The Royal Australian and New Zealand College of Psychiatrists
Downloaded By: [University Of South Australia Library] At: 09:02 20 August 2009
compare recent Australasian trends. Between 1990
and 1997, the production of methylphenidate in the
USA rose from 1788 kg to 13 824 kg, with the
majority of extra production being used for ADHD
treatment [12]. Estimates of the number of US
children using psychostimulants between 1987 to
1995 rose from 750 000 to 2 million [13,14]. Other
estimates claim a doubling in the number of children
between 1990 and 1995, and a further doubling by
2000 [15,16]. Recent estimates vary between a survey
of parents that reported 4.3% and a study that found
that 7.8% of children received psychostimulant
medication [17,18]. Specific details on the prevalence
of psychostimulant use are difficult to ascertain
because there is a high variation in national, regional
and local data [1921]. Some US estimates have been
as low as 0.4% in one county in New York [22], while
other estimates have been as high as 23% [23]. These
figures need to be viewed cautiously because a
number of factors may influence the variability in
psychostimulant rates [24], such as the problems of
data collected over different periods, with different
populations, across different locales, and with dis-
parate methods.
In the Australian context, between 1984 and 2000,
there was a 26% increase per year in the total rate of
consumption of dexamphetamine and methylpheni-
date per year, while from 1994 to 2000 the rate of
total psychostimulant consumption increased 8.46-
fold (compared with the period 19841993) [25].
Australia’s total consumption of dexamphetamine
during the period 19842000 for all States showed
an average increase of 31% per year and a 30% per
year increase for methylphenidate [25]. A recent study
in Western Australia found that the rate of stimulant
prescription was 2.35.3-fold greater in major cities
compared with remote and very remote parts of that
State [26]. In the present study the association
between socioeconomic disadvantage and the rate of
stimulant prescription was highly variable in different
jurisdictions [2729].
Other areas that lack clear data include which
Australian children are treated with psychostimulants
and for what duration. Although past studies suggest
that most students start psychostimulant use around
7 years of age [30,31] and that usage peaks at 9
10 years [32], there is still limited information about
the age at which children start treatment and the
duration of that treatment. Reports based on US
regional data estimate that duration of psychostimu-
lant treatment ranges between 8 years for high school
students and 5 years for middle school students [33],
with an average of 4 years for all students [2]. The
duration of psychostimulant treatment for most
children, however, essentially remains unknown.
Socioeconomic status (SES) has been identified as a
risk factor for ADHD diagnosis [34] (due to a link
with environmental or psychosocial stressors [35] and
the tendency of teachers to rate hyperactivity higher
in students of lower SES) [36,37], although there are
conflicting international accounts of the links be-
tween income and psychostimulant use [10,38,39]. In
the Australian context there are lower levels of
psychostimulant use among indigenous [40] and
Asian populations [41], while in New Zealand the
prevalence among the Maori population reflects that
of the broader population [42]. This also raises the
role of ethnicity in the acceptance of psychostimulant
treatment.
Throughout the 1990s Australia and New Zealand
closely paralleled the American increase in psychos-
timulant use [10,38,42]. In New Zealand, between
1992 and 2003 Ritalin prescriptions rose from just
under 3000 to almost 70 000 prescriptions, while
dexamphetamine prescriptions grew from B1000 to
around 5000 in the same period [42]. Currently, levels
of psychostimulant use in Australia and New Zealand
approximate those of the USA [11,27,28,43]. In
summary, there is an urgent need for studies that
provide more stable estimates of how many children
(with which demographic characteristics) are taking
psychostimulants for ADHD and for what duration.
This information has important clinical implications
in the integration and effective functioning of phar-
macological and other interventions.
In a previous paper we reported analysis of
psychostimulant use in the state of South Australia
for the period 19902000 [29]. This paper found that
the rate of prescriptions grew dramatically until 1995,
but then rates of psychostimulant use aligned with the
average for Australia as a whole [43]. We found that
demographic characteristics mirrored those of the
USA, with more boys medicated and the majority of
cases in the 59-year-old age range. In the study, the
median duration of psychostimulant use was approxi-
mately 2.5 years and there was pronounced geo-
graphic variability in prescription rates (which
significantly correlated with SES). Surprisingly, there
was also pronounced variability in the yearly rate of
new prescriptions as we documented a rapid increase
in the number of new prescriptions for psychostimu-
lants, along with a sharp decline after 1995.
In the present paper we revisit the South Australian
content to provide new data on psychostimulant use
covering the years 20012006. This allows compar-
isons between 19902000 (the period in which the
B. PROSSER, R. REID 341
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majority of psychostimulant treatment began), and
20012006 (the period in which psychostimulant
treatment had become well established). We report
data on yearly prescription rates, demographic in-
formation, duration of psychostimulant use and
geographic variation (including SES). We hypothe-
sized that (i) the demographic characteristics of
children in relation to starting age and male:female
ratio within this sample would not differ across the
two periods; (ii) the rate of new cases in this sample
would stabilize; and (iii) the correlation between low
SES and psychostimulant use would remain signifi-
cant for the period 20012006.
Methods
Data used for the present study were archival records of children
who received prescriptions for psychostimulants provided by the
South Australian Health Commission (SAHC). Psychostimulants
are classified as ‘drugs of dependence’ and in South Australia
medical practitioners are required to obtain an authorization from
the SAHC to treat a patient for periods 2 months. This data set
consisted of all children (birth18 years) who had been authorized
to receive psychostimulants in the city of Adelaide. Metropolitan
Adelaide has a population of 1 million people and comprises
70% of the total population of South Australia. Data for 7849
cases are presented spanning the periods 19902000 (5189 cases)
and 20012006 (2660 cases).
Data provided by the SAHC include gender, date of birth, date
of psychostimulant authorization, date of last contact (which
indicates when authorization ceased), postcode and status. Status
was defined by the SAHC as either ‘active’ (i.e. the child was
authorized to receive psychostimulants) or ‘ceased’ (i.e. the child
was no longer authorized to receive psychostimulants). From these
data we calculated the start age (date psychostimulants authorized
minus birthdate), duration (date ceased minus date psychostimu-
lant authorized), and the number of children beginning psychos-
timulants per year. Postcode was used as a geographic marker
because it covers a small and homogeneous population grouping.
There are 125 postcodes in the Adelaide metropolitan area. Eight
postcodes that cut across the metropolitan Adelaide boundary (and
covered a very small population) were excluded. The mean
population of the postcodes was 8607 (SD 1960).
Population and socioeconomic figures on postcodes were ob-
tained from the Australian Bureau of Statistics (ABS). For the
period 19902000 we used census data from 1996; for the period
20012006 we used census data from 2001. Standardized medica-
tion ratios (SMRs) for each postcode were computed using indirect
standardization. The ratio of observed counts to expected counts
for each postcode were derived by calculating agesex stratum-
specific proportions (using the entire Adelaide population as the
reference) and multiplying these proportions with the stratum-
specific populations and summing the product. The SMR for each
postcode was calculated by dividing the observed number of
children with prescriptions by the expected number (SMR 1
indicates more cases were observed than expected). To assess the
relation between SES and psychostimulant rates for postcodes, we
used the ABS Index of Relative Socioeconomic Disadvantage
(IRSD).[44] The IRSD considers factors such as educational levels,
income, and unemployment. A high score suggests that a postcode
has higher income families, more educated people and lower
unemployment.
Influencing the data was a shift in the status category used by the
SAHC to indicate whether a child was authorized to receive
psychostimulants midway through the 1990s. Until 1994, practi-
tioners were required to re-authorize treatments yearly. Due to an
increase in the number of authorizations that occurred throughout
the 1990s, the SAHC was unable to handle the volume of requests
on a yearly basis. This demand resulted in a change in policy. After
1994 physicians were no longer required to request yearly re-
authorizations, instead the initial authorization was valid until the
child reached the age of 18. Physicians were asked to report
voluntarily when a child ceased psychostimulants, but it is highly
unlikely that physicians reported all patients who had ceased. The
introduction of an improved data system by the SAHC in 2005
identified many inactive cases and deleted them. For this reason we
report duration data for only those who were reported to have
ceased.
Results
Table 1 provides a comparativeoverview of the results for the
periods 19902000 and 20012006.
Prescriptions by age group
Figure 1 shows the number of children per thousand of the
population beginning psychostimulants from 1990 to 2006 (accord-
ing to age group). The number of children receiving psychostimu-
lants increased markedly from 1990 to 1995, after which it began to
decline noticeably. Interestingly, in 2000 the number of new
authorizations approximated the numbers of 1992. In 2000 the
numbers again began to increase, a trend that continued until 2004.
Numbers decreased sharply, however, in both 2005 and 2006. As
expected, 59-year-olds received the majority of the new prescrip-
tions, followed closely by 1014-year-olds. These increases (and
decreases) in prescriptions by age were due to changes in the
number of boys receiving prescriptions, while rates for girls showed
a slower increase.
Prescription by gender
From 1990 to 2000 the overall male:female ratio was 5.4:1, while
from 20012006 the overall male:female ratio changed to 4.3:1. The
difference in male:female ratios across the two periods was
significant (x
2
7.8, p0.005, df 1). Thus, there was an overall
decline in male:female ratio during the period 19902006. There
was also considerable variability within each period. From 1992 to
2000 the male:female ratio exhibited a high of 7.7:1 (in 1993) and a
low of 4.3:1 (in 1998), but the changes within this period were
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statistically significant (x
2
22.63, p0.003, df 8; note: 1990 and
1991 were excluded due to low numbers). From 20012006 the
male:female ratio exhibited a high of 5.97:1 (in 2002) and a low of
3.46:1 (in 2006). Again the changes within the 20012006 period
were significant (x
2
11.27, p0.046, df 5).
Prescription by start age
Figure 2 shows a box plot of the median age at which children
began psychostimulants between 1992 and 2006 (1990 and 1991
were excluded due to low numbers). For the period 19902000, the
average age at which children started was 9.35 years (SD 3.25).
The average start age for boys and girls was 9.41 years (SD 3.21)
and 9.02 years (SD 3.39), respectively, while the difference
between the two was significant (F(
1,5188
)10.32, p0.001). For
the period 20012006 the average age at which children started was
8.84 years (SD2.88). The average start age for boys and girls,
respectively, was 8.74 years (SD 2.81) and 9.28 years (SD 3.15),
and again the difference was significant (F(
1,2658
)14.48,
pB0.001). Median start age varied between a low of 7.80 years
(in 2001) and a high of 9.87 years (in 1993). Results of a 2 (time
period)2 (gender) ANOVA showed that there was a significant
difference in start age across time periods (F(
1,7845
)4.40, p
0.036), and that there was a significant periodgender interaction
(F(
1,7845
)23.11, pB0.001). Thus, the average age of starting
psychostimulants declined slightly over the period 19902006, but
there was no significant main effect for gender.
Duration of psychostimulant treatment
From 1990 to 2000, 1688 children (1410 boys, 278 girls) were
reported as having ceased psychostimulant use. Of these cases, 945
(56%) were from the period 19901994 and 743 (44%) were from
19952000 (which is after the reporting procedure changed). For
those reported as ceased, the mean length of treatment for boys and
girls was 2.87 years (SD 1.94) and 2.85 years (SD 1.75), respec-
tively, and there was no significant difference between boys and
girls in treatment duration. Mean treatment length was 2.47 years.
For the years 20012006, 302 children (219 boys, 83 girls) were
reported as ceased. The mean length of treatment for boys and
girls, respectively, was 1.98 years (SD 1.64) and 2.27 years (SD
1.48) and the mean treatment length was 2.05 years. Although the
Table 1. Attention-deficithyperactivity disorder medication trends
South Australia
1990
2000
South Australia
2001
2006
USA
1990
2006
No. receiving
psychostimulants
19901995
Dramatic increase
20002004 Sharp increase 19901997 Dramatic
increase [12]
19952000 Steady
decline
20052006 Sharp
decline
19952000 Sharp
increase [16]
20002005 Steady
increase [18]
Male:female ratio 5.4:1 4.3:1 Ratio decrease [24]
Mean start age (years) 9.35 8.84 7 [31]
Mean duration of
treatment (years)
2.47 2.05 4 [2]
0
1
2
3
4
5
6
7
1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006
Year
Cases per 1000
0 -4 5 - 9 10 - 14 15 - 18
Age Group
Figure 1. Rate of new psychostimulant medication prescriptions per year by age group.
B. PROSSER, R. REID 343
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duration of treatment declined during the period 19902006, there
was no significant difference in treatment duration between boys
and girls.
Prescription by geographic variation
For the period 19902000, the SMRs of observed versus expected
rates by postcode ranged from 0.49 (indicating that only half as
many children as expected had received prescriptions) to 3.42
(indicating that more than threefold as many as would be
expected). Seventeen postcodes had significantly lower rates (p B
0.05) than would be expected and 16 had significantly higher rates
than expected (pB0.05). The Pearson correlation between SMR
and IRSD was significant (r 0.46, p B0.01). For 20012006 the
SMRs ranged from 0.15 (i.e. fewer than one-sixth of expected
children had received prescriptions) to 3.23 (i.e. more than
threefold as many as expected). The discrepancy between observed
and expected rates was significant for 25 of the postcodes: of these,
12 had significantly lower rates (pB0.05) than expected and 13 had
significantly higher rates than expected (p B0.05). The Pearson
correlation between SMR and IRSD was significant (r 0.36, p B
0.01). Thus, postcodes with lower SES were associated with
increased likelihood of receiving psychostimulants in both the
19902000 and 20012006 periods.
Discussion
The present results show that the demographics of
children in South Australia receiving psychostimu-
lants are similar to those of children in the USA. The
average age at which treatment began was consistent
with previous research, as was the increase with age,
peaking at age 9 or 10 years. The ratio of boys to girls
was also consistent with other studies. The male:fe-
male ratio exhibited considerable variability across
and within time periods, ranging from approximately
3:1 to 6:1. The overall trend, however, was toward a
lower male:female ratio. The age at which psychos-
timulant use started appears to be trending down-
ward as the mean start age decreased by
approximately 6 months between the 19902000 per-
iod and the 20012006 period. There were differences
across gender in start age. Although there was little
change in the mean start age for girls across the two
periods (9.02 vs 9.20), the male mean start age
decreased from 9.41 to 8.74 years. Thus, the trend
toward starting psychostimulants earlier was primar-
ily the result of increased numbers of boys receiving
at an earlier age. Increases in the rate of young
children receiving psychostimulants have been noted
previously [45], but the change in mean start age was
small (around 8 months).
One of the most surprising aspects of the data was
the variability in the rate of new cases per year. The
data included a large population and we expected
much more stability. The rapid increase in the period
from 1990 to 1995 can be explained when one
considers that the rate of psychostimulant authoriza-
tion for the decade prior to 1990 was essentially nil
(and rates were in effect catching up with the 35%
rate at which ADHD is thought to occur). After these
children had been accounted for, however, we ex-
pected that the rate would then decrease slightly and
Figure 2. Median age of starting psychostimulants (years) for 19922006.
344 CHANGES IN ADHD MEDICATION
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stabilize because the treatment population had been
identified and treated [26]. Instead, there was a
marked decrease across the two major age groups
(59- and 1014-year-olds) between 1995 and 2000.
This was followed by another increase (in 2004) to
reach near 1995 levels, which in turn was followed (in
2005) by an abrupt drop in numbers to those
approximating 1992 levels.
There is no obvious explanation for the changes
observed in the present study. One possible explana-
tion is that in each Australian State a relatively small
number of physicians can account for a dispropor-
tionate number of new prescriptions. For example in
Western Australia, five of 59 registered paediatricians
account for 26% of prescriptions statewide [46].
Changes in this group (e.g. relocations, retirement
etc.) could result in significant changes in the rate of
new psychostimulant prescriptions. Further, in small
and discrete urban communities such as Adelaide,
unique factors such as media reports, public events or
changes in policy [10,39] can have significant implica-
tions. Such factors are worthy of future research in
their own right.
In relation to duration of psychostimulant use,
results are consistent with recent reports that found
median duration to be approximately 2.5 years [45]
and that 36% of children discontinued within 1 year
[47]. The present data showed that half the children in
the subset reported receiving psychostimulant treat-
ment for B3 years. This finding has significant
treatment ramifications. Because children were most
likely to start medication before age 9, many will have
ceased psychostimulants before the end of primary/
elementary school. Studies in Australia also found
that current inclusive education policies struggle to
provide non-pharmacological resources for students
with ADHD behaviours [4850]. Further, in Austra-
lia only a small percentage of parents are able to
access school-based or mental health services for their
children, with costs of services and long waiting lists
frequently cited as barriers [51]. This suggests that
many students may receive no treatment for ADHD
for the majority of their time in school. We would
caution that the results from the 20012006 period
should be interpreted very judiciously due to the fact
that relatively few children were reported as ceased
compared to the previous period.
In relation to regional and socioeconomic varia-
tion, previous studies have reported distinct differ-
ences in the rate of psychostimulant use between
different countries [25] and across the USA [31,52].
There are also regional differences in Australia as is
demonstrated by a 2003 rate of psychostimulant use
in Western Australia that is double that of next
highest State and almost fourfold the national
average [2528]. The present results show that there
can also be considerable variation even within a
limited geographic area, such as the Adelaide metro-
politan area. There was a 20-fold difference between
the highest and lowest SMR in the present study, with
the correlation between SES and SMR significant for
both periods. The highest SMRs tended to be in areas
that are predominantly lower SES with high unem-
ployment. This result is consistent with that of the
Calver et al. study, which found that boys from
socioeconomically disadvantaged regions had higher
rates of psychostimulant use [26].
Limitations
The present data must be interpreted cautiously.
First, because of the changes in authorization proce-
dures there was no way to determine the number of
children who ceased psychostimulants after 1995. The
data show that the number of children reported as
ceased decreased markedly after 1994, but whether
this indicates an increased duration of psychostimu-
lant use or simply that physicians were not reporting
children who ceased treatment cannot be determined.
Thus, it is not possible to generalize the data from the
subset of children who were reported as having
ceased psychostimulants to the entire sample. Second,
these data do not include children who ceased within
1 month of starting medication and were not required
to be reported to the SAHC. Third, children who
ceased psychostimulants may have been switched to
other medications (e.g. antidepressants), which would
not be reflected in theses data. Finally, because of the
small numbers of student reported as ceased in the
20012006 period it is uncertain if the results would
generalize to the entire sample.
Finally, the present data addressed the relationship
between psychostimulant use, income, unemployment
and SES at the level of statistical region (which
approximately related to postcode). The data did not
address diagnosis, treatment and SES on the indivi-
dual level. Thus, it should be noted that there can be
significant variations in SES within statistical regions,
and although the present study suggests a correlation
between lower SES regions and higher rates of
medication use, it should not be assumed to be a
causal link between low-income families and psy-
chostimulant treatment.
B. PROSSER, R. REID 345
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Clinical implications
The data on duration of medication suggest that
significant numbers of children receive psychostimu-
lant treatment for ADHD for a relatively short
period, and many children may be untreated during
much of childhood and adolescence. Unless there are
other supports in place (e.g. educational accommoda-
tion, behaviour modification, counselling) there could
be increased risk for adverse outcomes. Further, if
medication is to be the mainstay of a treatment
programme, children must be maintained on an
appropriate (and properly monitored) course of
psychostimulants.
In sum, the present results suggest that the demo-
graphics of children receiving psychostimulants in
Australia are similar to those in the USA. Although
the magnitude of psychostimulant use is smaller, the
overall patterns of use across age and gender were
extremely consistent. The yearly rate of new cases,
however, is extremely variable and should receive
continued attention. Until now, duration of treat-
ment has received relatively little research, and the
present study indicates that it is an important aspect
of future treatment planning. Further, an under-
standing of why children cease psychostimulants
and how transitions are supported, as well as the
success of treatment should be the focus of future
research. Finally, the complex relationship between
SES and psychostimulant use remains largely unex-
plored and could provide important insights for more
effective and equitable treatment practices in the
future.
Acknowledgements
The authors thank Geoff Andersen, Senior Phar-
macist, Environmental Health Services, South Aus-
tralian Health Commission, SA Department of
Health.
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