Subtypes of Illicit Drug Users: A Latent Class Analysis of Data From an Australian Twin Sample

This article applies methods of latent class analysis (LCA) to data on lifetime illicit drug use in order to determine whether qualitatively distinct classes of illicit drug users can be identified. Self-report data on lifetime illicit drug use (cannabis, stimulants, hallucinogens, sedatives, inhalants, cocaine, opioids and solvents) collected from a sample of 6265 Australian twins (average age 30 years) were analyzed using LCA. Rates of childhood sexual and physical abuse, lifetime alcohol and tobacco dependence, symptoms of illicit drug abuse/dependence and psychiatric comorbidity were compared across classes using multinomial logistic regression. LCA identified a 5-class model: Class 1 (68.5%) had low risks of the use of all drugs except cannabis; Class 2 (17.8%) had moderate risks of the use of all drugs; Class 3 (6.6%) had high rates of cocaine, other stimulant and hallucinogen use but lower risks for the use of sedatives or opioids. Conversely, Class 4 (3.0%) had relatively low risks of cocaine, other stimulant or hallucinogen use but high rates of sedative and opioid use. Finally, Class 5 (4.2%) had uniformly high probabilities for the use of all drugs. Rates of psychiatric comorbidity were highest in the polydrug class although the sedative/opioid class had elevated rates of depression/suicidal behaviors and exposure to childhood abuse. Aggregation of population-level data may obscure important subgroup differences in patterns of illicit drug use and psychiatric comorbidity. Further exploration of a 'self-medicating' subgroup is needed.

Reasons for cannabis use in men with and without psychosis

Psychoses are relatively low prevalence disorders that have a disproportionately negative impact on individuals and society. Cannabis use is one factor that can exacerbate the negative consequences associated with psychotic disorders. Relatively few studies have examined the effects or reasons for using cannabis self-reported by individuals with psychosis. The present study is the first known to compare directly such factors in individuals with and without psychosis, within a single study. At baseline and follow-up participants with psychosis most commonly reported using cannabis for positive mood alteration (36% and 42%), coping with negative affect (27% and 29%) and for social activity reasons (38% and 29%). The control group most commonly reported using cannabis for relaxation (34% and 43%) and social activity reasons (49% and 51%). Participants with psychosis were less likely to report relaxation as the most important effect after use ( 27%) or expect it at follow-up ( 49%) compared to the control group (53% and 70%). In both groups, addiction and positive affect enhancement were the composite variable scores correlated most consistently with concurrent amount and frequency of use.

How common is comorbidity and why does it occur?

Comorbidity is most generally defined as the co-occurrence of two or more mental health problems. Comorbidity between drug and other psychological disorders has emerged as a major clinical, public health and research issue over the past few decades. The reasons for comorbidity are complex. Furthermore, comorbidity is often associated with poor treatment outcome, severe illness course, and high service utilisation. This presents a significant challenge with respect to the identification, prevention and management of people with comorbid disorders. The unmet need for treatment within this group is considerable and the lack of research is unacceptable. This paper will give a brief overview of epidemiological research into comorbidity; and examine the reasons why comorbidity might occur.

Is cannabis use a contributory cause of psychosis?

Objective: To assess whether cannabis use in adolescence and young adulthood is a contributory cause of schizophreniform psychosis in that it may precipitate psychosis in vulnerable individuals. Method: We reviewed longitudinal studies of adolescents and young adults that examined the relations between self-reported cannabis use and the risk of diagnosis with a psychosis or of reporting psychotic symptoms. We also reviewed studies that controlled for potential confounders, such as other forms of drug use and personal characteristics that predict an increased risk of psychosis. We assessed evidence for the biological plausibility of a contributory causal relation. Results: Evidence from 6 longitudinal studies in 5 countries shows that regular cannabis use predicts an increased risk of a schizophrenia diagnosis or of reporting symptoms of psychosis. These relations persisted after controlling for confounding variables, such as personal characteristics and other drug use. The relation did not seem to be a result of cannabis use to self-medicate symptoms of psychosis. A contributory causal relation is biologically plausible because psychotic disorders involve disturbances in the dopamine neurotransmitter systems with which the cannabinoid system interacts, as demonstrated by animal studies and one human provocation study. Conclusion: It is most plausible that cannabis use precipitates schizophrenia in individuals who are vulnerable because of a personal or family history of schizophrenia.

Drug use patterns and mental health of regular amphetamine users during a reported 'heroin drought'

Aims The present study extends the findings of a pilot study conducted among regular amphetamine users in Newcastle, NSW, in 1998. It compares key features between current participants in a state capital city (Brisbane) and a regional city (Newcastle) and between the 1998 and current Newcastle sample. Design Cross-sectional survey. Setting Brisbane and Newcastle, Australia. Participants The survey was conducted among 214 regular amphetamine users within the context of a randomized controlled trial of brief interventions for amphetamine use. Measurements Demographic characteristics, past and present alcohol and other drug use and mental health, treatment, amphetamine-related harms and severity of dependence. Findings The main findings were as follows: (i) the rate of mental health problems was high among regular amphetamine users and these problems commonly emerged after commencement of regular amphetamine use; (ii) there were regional differences in drug use with greater accessibility to a wider range of drugs in a state capital city and greater levels of injecting risk-taking behaviour outside the capital city environment; and (iii) there was a significant increase in level of amphetamine use and percentage of alcohol users, a trend for a higher level of amphetamine dependence and a significant reduction in the percentage of people using heroin and benzodiazepines among the 2002 Newcastle cohort compared to the 1998 cohort. Conclusions Further longitudinal research is needed to elucidate transitions from one drug type to another and from recreational to injecting and regular use and the relationship between drug use and mental health in prospective studies among users. Implications Intervention research should evaluate the effectiveness of interventions aimed at: preventing transition to injecting and regular use of amphetamines; toward reducing levels of depression among amphetamine users and interventions among people with severe psychopathology and personality disorders; and toward reducing the prevalence of tobacco dependence among amphetamine users.

Effects of reduction in heroin supply on injecting drug use: analysis of data from needle and syringe programmes

n early 2001 there was a dramatic decline in the availability of heroin in New South Wales (NSW), Australia, where previously heroin had been readily available at a low price and high purity.1 The decline was confirmed by Australia's strategic early warning system, which revealed a reduction in heroin supply across Australia and a considerable increase in price,2 particularly from January to April 2001. This "heroin shortage" provided a natural experiment in which to examine the effect of substantial changes in price and availability on injecting drug use and its associated harms in Australia's largest heroin market,2 a setting in which harm reduction strategies were widely used. Publicly funded needle and syringe programmes were introduced to Australia in 1987, and methadone maintenance programmes, which were established in the 1970s, were significantly expanded in 1985 and again in 1999.

Retrospections of a recovering drug researcher

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