Background: Ecstasy (MDMA) is distinguishable from other amphetamine-type stimulants such as methamphetamine by its novel combination of stimulant and hallucinogenic properties. During the 40 years since the first reported recreational use of Ecstasy, it has become well-established in the social environment of young adults in many countries. In Australia, Ecstasy use is more prevalent than use of any other illicit drug apart from cannabis. Despite its popularity, little is understood about the natural history of Ecstasy use, including reasons for the considerable uptake of use among young people. Consequently, there are shortcomings in policy and interventions tailored specifically to Ecstasy use, and ongoing debate concerning appropriate criminal justice responses. The natural history of drug use has profound implications for individual and population-level consequences of the use of different drugs. With regard to Ecstasy, basic questions remain unanswered, such as the proportion who are likely to develop problematic patterns of use and how long young users may persist with regular use. Stronger evidence in these areas may contribute to better policy and legislative responses. The Natural History Study of Drug Use (NHSDU), upon which this thesis is based, is the first Australian study to prospectively examine the natural history of Ecstasy use in a population sample of young adults.
Methods: In 2009 a sampling frame of Ecstasy users and non-users was developed for the NHSDU using population-based screening of drug use. A brief questionnaire assessing lifetime alcohol, tobacco, cannabis, amphetamines and Ecstasy use was mailed to 12,118 young adults randomly selected from the electoral roll. Respondents were 19-23 year old residents of Brisbane and the Gold Coast, Australia. Approximately 82% of eligible voters in this age group were registered on the electoral roll around the time of screening. The screening response rate was 49.9%. Using screening data, a probabilistic sample of 336 Ecstasy users (eligibility criteria of Ecstasy use on ≥ 3 occasions in the past 12 months) and a comparison group of 204 non-users (i.e. never used Ecstasy) was obtained. A retrospective/prospective longitudinal design is used to examine the natural history of Ecstasy use, with participant follow-up at 6, 12 and 30 months.
Objectives: This study investigates the natural history of Ecstasy use in an Australian young adult population cohort, beginning with early exposure to Ecstasy use. The specific objectives include 1) the trialling of population screening as a means of developing a sampling frame of Ecstasy users and non-users, and the derivation of estimates of drug use prevalence from the screening data to assess the viability of population screening and provide contextual information; 2) comparing the prevalence of exposure to Ecstasy offers among young adult Ecstasy users and non-users, and evaluating predictors of Ecstasy-naive young adults’ exposure to offers; 3) examining the extent to which the recreational social environment contributes to Ecstasy use initiation in early adulthood independently of individual risk factors; 4) identifying Ecstasy use trajectories over a 30 month period during early adulthood and the proportion involved in each trajectory, and assessment of predictors of trajectory group membership; 5) examining the relationship between psychological distress and patterns of drug use among Ecstasy users, with consideration of how different sampling methods affect estimates of association.
Findings: Exposure to Ecstasy offers is common in recent age cohorts of young Australian adults, with nearly half of non-users ever receiving an offer. The high prevalence of offers is linked to the pervasiveness of Ecstasy-using social contacts among young adults and exposure to offers occurs independently of risk factors such as early drug use and delinquency. Contextual social factors, including knowing >10 Ecstasy users (Adjusted Relative Risk 3.15, 95% CI 1.57-6.34) and recurrently attending electronic/dance music events (ARR 6.97, 95% CI 1.99-24.37) are robust predictors of Ecstasy use initiation. Psychological distress (ARR 5.34, 95% CI 2.31-12.33) and early cannabis use (age < 15 years; ARR 4.04, 95% CI 1.78-9.17) are also independently associated with initiation. However, compared to contextual social factors, the proportion of Ecstasy initiation attributable to these two factors is relatively small. Three distinct Ecstasy use trajectories were identified using cluster analysis: low-use (35.7%), intermediate (56.2%) and high-use (8.1%). These trajectories are characterised by low or declining levels of use within a 30-month period. At its peak the high-use trajectory involved 1-2 days of Ecstasy use per week on average. Perceived changes in Ecstasy quality contributed modestly to decreases in frequency of use, but overall, market factors did not appear to have any great impact. Attendance at electronic/dance music events (ARR 4.12, 95% 1.48-11.46) and experiencing consistently positive subjective effects (e.g. being talkative, increased empathy, being very friendly, increased libido) at baseline predicted high-use trajectory membership (ARR 3.18, 95% CI 1.17-8.64). Relatively few Ecstasy users (11.8% at baseline and 5.7% at 12 months) reported negative subjective effects (e.g. anxiety, paranoia, aggression, depression) over multiple occasions of use. Ecstasy use trajectories are not significantly associated with Ecstasy dependence (DSM-IV) and few users (5.7%) reported recent (12-month) Ecstasy dependence. No association was found between psychological distress and trajectory membership. However, daily tobacco smoking is associated with psychological distress in this population (Adjusted Odds Ratio: 2.16, 95% CI 1.05-4.42) and one-third of Ecstasy users are daily smokers.
Conclusions: The considerable exposure of non-users to Ecstasy offers reflects a large degree of social interaction between users and non-users and is also suggestive of considerable social acceptance of Ecstasy use among young adults. Both the initiation of Ecstasy use and involvement in the most intensive trajectories of Ecstasy use is mainly attributable to aspects of young adults’ social environment, including contact with Ecstasy-using friends and engagement in cultural activities and settings where Ecstasy is used. Ecstasy use trajectories are also influenced by users’ initial experience of subjective effects, related to physical and emotional intimacy, and appear to be independent of risk factors such as aggression, delinquency and drug dependence. We observed rapid decreases in use which are likely to represent some degree of systematic change, especially given that frequent use was largely confined to recent initiates. Thus, Ecstasy use could be characterised as an ‘instrumental’ pattern of behaviour with regard to young adults’ age-relevant goals. We also found evidence of a direct pathway from psychological distress to Ecstasy initiation for a small proportion of users, but these young adults were no more likely than other Ecstasy users to progress to heavy patterns of use. The low intensity of young adults’ Ecstasy use trajectories suggests that the associated health and social burden is of a limited magnitude, and provides additional support for evidence-based drug rankings indicating that Ecstasy is relatively benign. Despite the constrained nature of Ecstasy trajectories, young adults may be exposed to risks in the short-term, including acute toxicity due to drug combinations and behaviours such as drug-impaired driving. Because of the high prevalence of Ecstasy offers, universal education strategies may be required to inform potential users of these harms. Young adult Ecstasy users are also an important target population for integrated smoking cessation and mental health initiatives.