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| Journal of the New Zealand Medical Association,
27-October-2006, Vol 119 No 1244
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Recent population trends in amphetamine use in
New Zealand: comparisons of findings from national household drug surveying
in 1998, 2001, and 2003
Chris Wilkins, Paul Sweetsur, Sally Casswell
Since the late 1990s, New Zealand has experienced dramatic
increases in detections of potent amphetamines, such as
methamphetamine.1 The number of clandestine
amphetamine laboratories detected each year by the New Zealand Police increased
from just 2 in 1998, to 41 in 2001, and to 202 in
2003.2,3 Related to the increase in clandestine
amphetamine manufacture, there were increased seizures of ephedrine tablets
which are used to synthesis amphetamine, made by the New Zealand Customs Service
from 10,308 tablets in 2000, to 32,653 tablets in 2001, to 830,320 tablets in
2003.3,4 Trends in drug seizures, however, can
be influenced by the resources and attention dedicated to a drug type by law
enforcement agencies, and consequently they are not necessarily an accurate
measure of population trends in the use of a drug.
International studies have shown that chronic or high-dose
use of amphetamines can cause hostility, violence, audio and visual
hallucinations, and a paranoid psychosis resembling schizophrenia. In addition
they can cause damage to cardiac, vascular, and neurological
systems.5–10
In New Zealand, the growing use of amphetamine has been
linked to a range of public health and social problems including mental illness,
drug dependence, intravenous drug use, family break-down, violence, and property
crime.2,11,12,13
The continued rise in detections of local amphetamine
laboratories and related precursor chemicals since 2001 has led to considerable
public anxiety about the eventual level of amphetamine use in New Zealand. For
example, some sources quoted by the popular media have suggested that
amphetamine use may continue to increase to a point where it replaced cannabis
as New Zealand’s most widely used illicit
drug.19
In 2002, the government and law enforcement agencies
initiated several legislative and strategic responses to the rise in amphetamine
use, with a particular focus on domestic methamphetamine manufacture and
use.3
The aim of this paper is to track recent trends in the
population prevalence, availability, price, and harm of amphetamine in New
Zealand. The analysis is carried out using data from the three most recent waves
of New Zealand national household drug surveying conducted in 1998, 2001, and
2003 respectively.
MethodNational household drug surveying was conducted in New
Zealand in 1998, 2001, and 2003. The 1998 and 2001 surveys were funded from
contestable research funds and were known as the National Drug Survey (NDS). The
2003 wave of surveying was directly funded by the Ministry of Health and was
renamed the Health Behaviours Survey-Drug Use (2003 HBS-Drug Use). The 2003
HBS-Drug Use retained the same Computer Assisted Telephone Interview (CATI)
survey methodology and core sections of the questionnaire from the NDS. The age
range of the 2003 HBS-Drug Use sample was extended from the age ranges surveyed
by the NDS (i.e. 15–45 years in 1998 and 13–45 years in 2001) to
include 13–65 year olds.
To allow valid comparisons back to the 1998 NDS, the
age range of the 2003 HBS-Drug Use sample and 2001 NDS sample were truncated to
those aged 15–45 years old. The 1998 NDS and 2003 HBS-Drug Use included
extended samples of Maori to allow detailed comparisons of Maori and non-Maori.
To ensure valid comparisons between all three survey
waves, only the general population random digit dial (RDD) samples from each
survey wave were compared. Interviewing for the RDD sampling was conducted
between April and September in each survey wave to replicate any seasonal
variation in drug use.
All three waves of RDD sampling employed the same CATI
sampling methodology. Telephone numbers were selected using a stratified random
digit dialling method so that each household, of a particular stratum,
nationwide had an equal chance of being called. The country was divided into a
number of strata based on telephone exchanges to represent the different
socioeconomic characteristics of the population. A proportionate sample from
each stratum was then taken.
Within each household, one person was randomly selected
for an interview. Each telephone number was tried at least 10 times on different
dates and times of the day in an effort to reach those seldom at home.
Respondents were informed that the study was being conducted on behalf of the
Ministry of Health and that everything they said would be confidential.
In each survey wave, participants were asked the same
questions concerning whether they had ever used amphetamine and whether they had
used amphetamine in the last 12 months. The questions about amphetamine referred
to the broad class of the amphetamines which the interviewer described to the
respondent as ‘amphetamines, uppers, speed, methamphetamine’.
Additional questions on amphetamine were included in
the 2001 and 2003 waves of surveying, including questions on whether the
availability and price of amphetamine had changed compared to 12 months ago, and
whether the use of amphetamine had harmed eight areas of a user’s life in
the previous 12 months. The respective sample sizes for each survey wave were:
5475 in 1998; 5504 in 2001 and 3042 in 2003. The response rates for the survey
waves were 79% in 1998, 80% in 2001, and 68% in 2003. (This is the response rate
for the general sample of 2003 HBS-Drugs which was collected in the age range
13–65 years old. It was not possible to recalculate the response rate for
the truncated age range as we could not distinguish the non-response by
age.)
AnalysisAll three samples were weighted by the number of people
within the household who were eligible for each survey to adjust for the
selection of only one person per household. Prevalence levels and confidence
intervals were calculated using logistic regression, accounting for the effects
of weighting and stratification.
Two sample t-tests were used, based on the logistic
regression summary statistics, to test for differences between the samples.
There were three t-tests per prevalence level; one for each two-way combination
of the three samples. When comparing more than two groups, the probability of
making a type 1 error increases if not adjusted for. Consequently when
comparisons were made between the 3 years, values are only reported as
significant when the p value <0.017. This value was calculating using the
Sidak-Bonferroni method.
 where
 is the desired overall alpha level and n is the number of
groupsIn this case
 Where comparisons are only made between two survey
years, differences have been reported if the p value <0.05. The error bars on
the graphs indicate the 95% confidence intervals. All analysis was run in the
SAS and SUDAAN statistical software packages.
ResultsPrevalence of amphetamine use—The
proportion of the sample who had ever used amphetamine increased in 2001
compared to 1998 (11.0% versus 7.6%, p<0.0001) and then decreased in 2003
compared to 2001 (9.0% versus 11.0%, p=0.0066). By age group, there was an
increase in those who had ever tried amphetamine in 2001 compared to 1998 among
those aged 20–24 years old (from 16.2% versus 8.5%, p<0.0001).
The last-year use of amphetamine increased in 2001 compared
to 1998 (5.0% versus 2.9%, p<0.0001) and then did not change in 2003 compared
to 2001 (4.0% versus 5.0%, p=0.0466). The last-year use of amphetamine increased
between 1998 and 2001 for those aged 15–19 years old (4.0% versus 7.5%,
p=0.0078), 20–24 years old (5.8% versus 10.5%, p=0.004), and 35-45 years
old (0.6% versus 1.5%, p=0.0084) (Figure 1).
Change in the availability of
amphetamine—The proportion of those who had used amphetamine in
the last year who said that the availability of amphetamine had become
‘harder’ compared to 12 months ago was higher in 2003 compared to
2001 (24.5% versus 12.4%, p=0.0284) (Figure 2). In 2003, as in 2001, nearly half
of the last-year amphetamine users reported the availability of amphetamine was
‘easier’ compared to a year ago. In 2003, 3 out of 10 (29.0%)
last-year amphetamine users reported the availability of amphetamine was the
‘same’ as a year ago.
Figure 1. Last year use of amphetamine by age,
1998, 2001, and 2003
 Figure 2. Change in the availability of
amphetamine compared to a year ago, 2001, and 2003
 Change in price of amphetamine—There was no change in
the perceptions of the price of amphetamine by last-year amphetamine users in
2003 compared to 2001. In 2003, 6 out of 10 last-year amphetamine users (61.7%)
described the price of amphetamine as the ‘same’ compared to a year
ago; 1 in 4 (24.8%) last-year amphetamine users said the price was
‘lower’ and 1 in 8 (13.4%) said the price was ‘higher’
compared to a year ago.
Harms from amphetamine use—There was
no difference in the proportion of last-year amphetamine users reporting harm in
different areas of their life from amphetamine use in 2003 compared to 2001
(Table 1).
Table 1. Last-year amphetamine users who
reported areas of their life harmed from amphetamine use in the last 12
months
In 2003, as in 2001, harm to ‘energy and
vitality’, ‘financial position’, and ‘health’ were
the areas of life most commonly reported harmed from amphetamine use. Three out
of 10 of those who had used amphetamine in the last year had experienced harm to
at least one of the areas of life asked about in both 2001 and 2003.
DiscussionThe comparisons of the three waves of New Zealand national
household drug surveying indicate a general rise in the initiation of (and
last-year use of) amphetamine use in New Zealand in 2001 compared to 1998. This
was followed by a levelling out in levels of last-year use of amphetamine in
2003 compared to 2001.
In 2003, more last-year amphetamine users reported that the
availability of amphetamine had become more difficult compared to the preceding
12 months, than in 2001. However, in 2003, as in 2001, nearly half of the users
reported that the availability of amphetamine had become ‘easier’
compared to a year ago.
Approximately 6 out of 10 last-year users in 2001 and 2003
reported the price of amphetamine was the ‘same’ compared to 12
months ago. Similar proportions of last-year amphetamine users reported harm in
different areas of their life in 2001 and 2003 from their amphetamine use. In
both survey waves, approximately 1 in 5 last-year users reported harm to
‘energy and vitality’(and 1 in 10 reported harm to
‘health’) due to their amphetamine use in the last 12 months.
The validity of the comparisons between the waves of
national household drug surveying relies on the exact replication of the survey
methodology for each wave. This ensures that any differences found between the
waves represent real changes in drug use and are not due to any change in the
way the survey was conducted.
As detailed in the methodology section, all three RDD
general population samples employed the same CATI survey methodology, asked the
same questions about amphetamine use, and were collected during the same months
of the year. The extended age ranges of the 2003 HBS-Drug Use and 2001 NDS were
truncated to match the 15–45 year olds surveyed in the 1998 NDS.
While replication of the CATI survey methodology allows
valid comparisons between the survey waves, we acknowledge that household drug
surveys in general are likely to underestimate the true extent of drug use to
some extent. This is largely due to the difficulties of reaching heavier drug
users who are more likely to be homeless, incarcerated, or be difficult to
contact in general.31
There were some differences between the survey waves in
regard to the performance of the survey methodology. The response rate of the
survey fell in 2003 compared to previous years. One factor in the decline in the
response rate of the survey may have been the increase in private telephone
market surveying in New Zealand over this time, which inadvertently competes
with social science surveying for respondents’ time and patience. It might
be speculated that drug users may be less likely to want to participate in the
survey and consequently are more likely to be non-responders.
Increasing stigmatisation of methamphetamine as result of a
number of high-profile violent crimes attributed to methamphetamine use and
psychosis, and the reclassification of methamphetamine to Class A, may have also
contributed to declining response rates and willingness to admit amphetamine
use. The higher non-response in 2003 may have caused some underestimation of
drug use in 2003 compared to other years. However, given the magnitude of the
difference in non-response between 2003 and 2001 (i.e. 12%), even assuming a
much higher prevalence of amphetamine use among the non-responders compared to
the survey sample, it would be unlikely to change the outcome of the statistical
tests. The last-year use of amphetamine among the non-responders in 2003 would
have to be over 15% (compared to 4% within the responders) to result in a
statistically significant increase in amphetamine use in 2003 compared to
2001.
In each wave of the survey, the age, gender, and ethnicity
of the survey sample was compared with respective Census population figures or
(where appropriate) Census population
estimates.14,15 In the 1998 and 2001 waves, the
weighted survey sample had a slightly higher proportion of males than the Census
population figures. About two-thirds of amphetamine users in each survey wave
were male,12,16,17 so the lower proportion of
males in the weighted sample in 2003 compared to previous waves may have caused
a very small underestimation of amphetamine use. Again these differences were
not considered large enough to make a difference to the results of the
statistical tests completed.
Two types of environmental change may have played a part in
the stabilisation of use (and the relative decline in levels of availability) of
amphetamine in New Zealand in 2003 compared to 2001. The first is a growing
awareness among the youth and drug-using population concerning the health risks
and disutility of methamphetamine use over the medium and long term. Chronic
heavy methamphetamine users are at high risk of experiencing serious
psychological problems from their drug use, such as acute psychosis, extreme
paranoia, aggression, and dependence.8,20
A recent convenience sample of frequent methamphetamine
users (n=78) interviewed from five centres in New Zealand found that 58%
reported ‘short temper’, 56% ‘paranoia’, 51%
‘anxiety’, 43% ‘depression’, and 22% ‘suicidal
thoughts’ related to their methamphetamine use in the last 6
months.32
In 2002, methamphetamine use was implicated in a series of
rather bizarre and extremely violent crimes in New Zealand committed by
individuals under the influence of methamphetamine or suffering
methamphetamine-induced psychosis. These crimes included a multiple homicide,
unprovoked stranger murder, and samurai sword attack and murder. These criminal
incidents and their link with the newly emerging methamphetamine received
extensive coverage in the local media.19
Studies of amphetamine users in other countries have found
that the negative mental health effects of amphetamine-use (such as aggression,
paranoia, and depression), rather than physical harms from use, were the
problems that caused the greatest concern among users and were most likely to
cause them to seek help for their drug use.20
This sensitivity was thought to be related to the value young people placed on
acceptance by their peer group and the effect that behavioural abnormalities
could have on these relationships.20
The highly publicised mental health effects of
methamphetamine use may have damaged the reputation of methamphetamine as a
manageable risk among some drug users and young people in New Zealand after
2001. A drug’s reputation or image is considered to be central to fuelling
a drug epidemic by encouraging the curious to start use, and reinforcing current
users desire to continue and escalate their
use.21–23
Accounts of amphetamine trends in Japan, Australia, and the
United States have identified the relative rapidity with which new amphetamine
users discover the negative mental health effects of amphetamine use, and the
often shocking criminal incidents associated with amphetamine-induced psychosis,
as factors which have tended to contribute to the relative short time span of
amphetamine epidemics.21,24–26
Secondly, following the rise in amphetamine use in 2001
there was a concerted law enforcement and legislative response to this drug type
in New Zealand, with a particular focus on the locally manufactured
methamphetamine.3
New Zealand Police negotiated a series of protocols with the
Pharmaceutical Guild to control and monitor the over-the-counter sale of
ephedrine-based flu medicines from pharmacies, as these products were been used
as sources of ephedrine to synthesis
methamphetamine.4
Three specialised police teams were established in 2002 to
detect and dismantle clandestine methamphetamine
laboratories.3 With the emergence of
large-scale domestic methamphetamine manufacture, New Zealand Customs paid
greater attention to the importation of ephedrine, products containing
ephedrine, and other chemical precursors used in methamphetamine manufacture.
In early 2003, the New Zealand Parliament reclassified
methamphetamine (from a Class B to a Class A drug offence) under the Misuse
of Drugs Act 1975. A Class A drug offence is the highest offence class; it
carries a maximum penalty of life imprisonment for trafficking and manufacture.
Changes to the Misuse of Drugs Act 1975 were also
enacted to increase the powers of the police and customs to search and seize
unlicensed imports of ephedrine and other chemicals used to synthesis
methamphetamine. A strong law enforcement and legislative response to a sudden
rise in amphetamine use has been discussed as a factor which has assisted in the
control of outbreaks of amphetamine use in other countries at other
times.23,24,26–30
Amphetamine remains a drug of serious concern in New
Zealand. As noted here, chronic heavy methamphetamine use is associated with
aggression and serious psychological problems with implications for violence,
crime, and neglect of responsibility.
One in 10 New Zealanders aged 20–24 years old had used
amphetamine in the last year in 2003, and approximately 3 out 10 last-year users
experience harm in at least one area of their life in the preceding 12 months.
There is evidence of a levelling out in the prevalence of amphetamine use and
some evidence of a relative decline in the availability of amphetamine in New
Zealand. This may reflect greater awareness of the health risks of
methamphetamine use and a greater law enforcement focus on methamphetamine in
recent years. The levelling out of amphetamine use in 2003 may well be only a
temporary phenomenon, however.
The impact of the shocking criminal incidents and stiffer
regulatory controls related to amphetamine may fade over the coming years. A
number of countries which have historically had problems with amphetamine use
have experienced recurring amphetamine epidemics as new generations of young
people rediscover the attractive features of amphetamine while having little
sub-cultural memory of the hazards of
use.23–25,28,30
Acknowledgements:
We acknowledge several funding sources and individuals who made this
analysis possible. The 2003 National Household Drug Survey was reconfigured as
the 2003 Health Behaviours Survey–Drug Use Survey and was funded by the
Ministry of Health and carried out as part of the Public Health Intelligence
(PHI) Health Behaviours Survey Monitor. The statistical design and analysis for
the 2003 survey was completed by Megan Pledger and Paul Sweetsur at the Centre
for Social and Health Outcomes Research and Evaluation (SHORE), Massey
University, and by James Reilly at Statistical-Insights.
Data collection was managed
by Chris Wilkins, Rachael Lane, Joe Morley, and Mary Blade. The 2001 New Zealand
National Drug Survey was a project of the Alcohol & Public Health Research
Unit (APHRU) at the University of Auckland, and was funded by the Health
Research Council (HRC) and the Alcohol Advisory Council of New Zealand.
The funding to conduct the
survey was awarded to Sally Casswell as an investigator-initiated research
grant. The 2001 survey was led by Chris Wilkins with Rachael Lane, Mary Blade,
and Heather Seal. The data management and weighting for the 2001 survey were
carried out by Krishna Bhatta and Megan Pledger (assisted by Michael Ford and
Alistair Stewart).
The 1998 New Zealand National
Drug Survey was a project of the APHRU at the University of Auckland, and was
funded as a core programme of the HRC and the Alcohol Advisory Council. The
funding to conduct the survey was provided in part by the HRC as an
investigator-initiated research grant to Sally Casswell, and in part by the
Ministry of Health.
The 1998 survey was led by
Adrian Field with Brendon Dacey and Francesa Holibar. The data management and
weighting for the 1998 survey were carried out by Jia-fang Zhang, Michael Ford,
and Krishna Bhatta (assisted by Allan Wyllie).
Subsequent secondary analysis
of the three national household drug surveys was funded by New Zealand Police in
2005. Last but not least, we acknowledge the time and willingness of the New
Zealand public to respond to all the survey waves, without which none of the
surveys would have taken place.
Author information: Chris Wilkins, Senior
Researcher; Paul Sweetsur, Statistician; Sally Casswell, Director; Centre for
Social and Health Outcomes Research and Evaluation (SHORE), Massey University,
Auckland
Correspondence: Dr Chris Wilkins, Centre
for Social and Health Outcomes Research and Evaluation (SHORE), Massey
University, PO Box 6137, Wellesley Street, Auckland. Fax: (09) 366 5149; email:
c.wilkins@massey.ac.nz.
References:
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