Changes in cannabis potency and first-time admissions to drug treatment: a 16-year study in the Netherlands.

BACKGROUND: The number of people entering specialist drug treatment for cannabis problems has increased considerably in recent years. The reasons for this are unclear, but rising cannabis potency could be a contributing factor. METHODS: Cannabis potency data were obtained from an ongoing monitoring programme in the Netherlands. We analysed concentrations of δ-9-tetrahydrocannabinol (THC) from the most popular variety of domestic herbal cannabis sold in each retail outlet (2000-2015). Mixed effects linear regression models examined time-dependent associations between THC and first-time cannabis admissions to specialist drug treatment. Candidate time lags were 0-10 years, based on normative European drug treatment data. RESULTS: THC increased from a mean (95% CI) of 8.62 (7.97-9.27) to 20.38 (19.09-21.67) from 2000 to 2004 and then decreased to 15.31 (14.24-16.38) in 2015. First-time cannabis admissions (per 100 000 inhabitants) rose from 7.08 to 26.36 from 2000 to 2010, and then decreased to 19.82 in 2015. THC was positively associated with treatment entry at lags of 0-9 years, with the strongest association at 5 years, b = 0.370 (0.317-0.424), p < 0.0001. After adjusting for age, sex and non-cannabis drug treatment admissions, these positive associations were attenuated but remained statistically significant at lags of 5-7 years and were again strongest at 5 years, b = 0.082 (0.052-0.111), p < 0.0001. CONCLUSIONS: In this 16-year observational study, we found positive time-dependent associations between changes in cannabis potency and first-time cannabis admissions to drug treatment. These associations are biologically plausible, but their strength after adjustment suggests that other factors are also important.

A place to call home: study protocol for a longitudinal, mixed methods evaluation of two housing first adaptations in Sydney, Australia.

BACKGROUND: This protocol describes a study evaluating two 'Housing First' programs, Platform 70 and Common Ground, presently being implemented in the inner-city region of Sydney, Australia. The Housing First approach prioritises housing individuals who are homeless in standard lease agreement tenancies as rapidly as possible to lock in the benefits from long-term accommodation, even where the person may not be seen as 'housing ready'. METHODS/DESIGN: The longitudinal, mixed methods evaluation utilises both quantitative and qualitative data collected at baseline and 12-month follow-up time points. For the quantitative component, clients of each program were invited to complete client surveys that reported on several factors associated with chronic homelessness and were hypothesised to improve under stable housing, including physical and mental health status and treatment rates, quality of life, substance use patterns, and contact with the health and criminal justice systems. Semi-structured interviews with clients and stakeholders comprised the qualitative component and focused on individual experiences with, and perceptions of, the two programs. In addition, program data on housing stability, rental subsidies and support levels provided to clients by agencies was collected and will be used in conjunction with the client survey data to undertake an economic evaluation of the two programs. DISCUSSION: This study will systematically evaluate the efficacy of a scatter site model (Platform 70) and a congregated model (Common Ground) of the Housing First approach; an examination that has not yet been made either in Australia or internationally. A clear strength of the study is its timing. It was designed and implemented as the programs in question themselves were introduced. Moreover, the programs were introduced when the Australian Government, with State and Territory support, began a more focused, coordinated response to homelessness and funded rapid expansion of innovative homelessness programs across the country, including Common Ground supportive housing developments.

Does the social context of early alcohol use affect risky drinking in adolescents? Prospective cohort study.

BACKGROUND: There are limited longitudinal data on the associations between different social contexts of alcohol use and risky adolescent drinking. METHODS: Australian prospective longitudinal cohort of 1943 adolescents with 6 assessment waves at ages 14-17 years. Drinkers were asked where and how frequently they drank. Contexts were: at home with family, at home alone, at a party with friends, in a park/car, or at a bar/nightclub. The outcomes were prevalence and incidence of risky drinking (≥5 standard drinks (10g alcohol) on a day, past week) and very risky drinking (>20 standard drinks for males and >11 for females) in early (waves 1-2) and late (waves 3-6) adolescence. RESULTS: Forty-four percent (95 % CI: 41-46 %) reported past-week risky drinking on at least one wave during adolescence (waves 1-6). Drinking at a party was the most common repeated drinking context in early adolescence (28 %, 95 % CI 26-30 %); 15 % reported drinking repeatedly (3+ times) with their family in early adolescence (95 % CI: 14-17 %). For all contexts (including drinking with family), drinking 3+ times in a given context was associated with increased the risk of risky drinking in later adolescence. These effects remained apparent after adjustment for potential confounders (e.g. for drinking with family, adjusted RR 1.9; 95 % CI: 1.5-2.4). Similar patterns were observed for very risky drinking. CONCLUSIONS: Our results suggest that consumption with family does not protect against risky drinking. Furthermore, parents who wish to minimise high risk drinking by their adolescent children might also limit their children's opportunities to consume alcohol in unsupervised settings.

Prevalence, correlates and comorbidity of DSM-IV Cannabis Use and Cannabis Use Disorders in Australia.

OBJECTIVE: To report nationally representative findings on the prevalence, correlates, psychiatric comorbidity and treatment of DSM-IV Cannabis Use and Cannabis Use Disorders in Australia. METHOD: The 2007 National Survey of Mental Health and Wellbeing was a nationally representative household survey of 8841 Australians (16-85 years) that assessed symptoms of the most prevalent DSM-IV mental disorders. RESULTS: Prevalence of lifetime and 12-month cannabis use was 18% and 6%; prevalence of lifetime and 12-month cannabis use disorder was 6% and 1%. The conditional prevalence (proportion of ever users who met criteria for a disorder) of lifetime and 12-month cannabis use disorder was 32.2% and 14.3%. Current cannabis use disorders were more common in males (OR 2.0) and younger users (OR 4.6). Strong associations were observed between current cannabis use disorders and alcohol use disorders (OR 3.6) and current affective disorders (OR 3.0). Only 36.2% of those with current cannabis use disorders sought any treatment. CONCLUSIONS: The prevalence of cannabis use disorders in the Australian population is comparable with that in the USA. Current cannabis use disorders are highly concentrated in young Australians who have high levels of comorbidity. The low rates of treatment seeking warrant attention in treatment and prevention strategies.

Definition matters: assessment of tolerance to the effects of alcohol in a prospective cohort study of emerging adults.

BACKGROUND AND AIMS: Tolerance to the effects of alcohol is an important element in the diagnosis of alcohol use disorders (AUD); however, there is ongoing debate about its utility in the diagnosis AUD in adolescents and young adults. This study aimed to refine the assessment of tolerance in young adults by testing different definitions of tolerance and their associations with longitudinal AUD outcomes. DESIGN: Prospective cohort study. SETTINGS: Australia. PARTICIPANTS: A contemporary cohort of emerging adults across Australia (n = 565, mean age = 18.9, range = 18-21 at baseline). MEASUREMENTS: Clinician-administered Structured Clinical Interview for DSM-IV Research Version (SCID-IV-RV) assessed for AUD criteria across five interviews, at 6-month intervals over 2.5 years. Tolerance definitions were operationalized using survey-type response (yes/no), clinician judgement (SCID-IV-RV), different initial drinking quantity and percentage increase thresholds and average heavy consumption metrics. AUD persistence was operationalized by the number of times AUD was present across the 2.5-year study period (n = 491), and new-onset AUD was operationalized as any new incidence of AUD during the follow-up period (n = 461). FINDINGS: The (i) SCID-IV-RV clinician judgement [odds ratio (OR) = 2.50, P = 0.005], (ii) an initial drinking quantity threshold of four to five drinks and 50% minimum increase (OR = 2.48, P = 0.007) and (iii) 50% increase only (OR = 2.40, P = 0.005) were the tolerance definitions more strongly associated with any new onset of AUD throughout the four follow-up time-points than other definitions. However, these definitions were not associated with persistent AUD (Ps > 0.05). Average heavy consumption definitions of tolerance were most strongly associated with persistent AUD (OR = 6.66, P = 0.001; OR = 4.65, P = 0.004) but not associated with new-onset AUD (Ps > 0.05). CONCLUSIONS: Initial drink and percentage change thresholds appear to improve the efficacy of change-based tolerance as an indicator for new-onset alcohol use disorder diagnosis in self-report surveys of young adults. When predicting persistent alcohol use disorder, average heavy consumption-based indicators appear to be a better way to measure tolerance than self-reported change-based definitions.

Trends in cannabis use and attitudes toward legalization and use among Australians from 2001-2016: an age-period-cohort analysis.

BACKGROUND AND AIMS: Changes in cannabis legalization and availability in Australia necessitate monitoring use and attitudes. We estimated age-period-cohort effects of past-year cannabis use and attitudes toward criminalization and legalization. DESIGN: Analysis of six waves of the Australian National Drug Strategy Household Survey (NDSHS) every 3 years (2001-2016). SETTING AND PARTICIPANTS: The study was nationally representative of Australian households using multistage random sampling, totaling 145 168 respondents 18-79 years old. Data were collected using telephone, face-to-face, and drop-and-collect. Sample sizes per analysis varied based on data availability (~107 000-127 000 per model). MEASUREMENTS: Six waves of data for past-year cannabis use (by sex and education), attitudes toward criminalization and legalization. FINDINGS: Past-year cannabis use decreased in young adults ages 18-35 from 2001-2016 (25.1%-18.6%) and increased in middle adults ages 36-55 (8.6%-10.1%) and older adults ages 56-79 (0.6%-3.0%). We observed a positive period effect and negative cohort effect for recent cohorts for past-year use (e.g. 1955 cohort had 1.41 (95% CI: [1.11, 1.70]) increased log odds vs. 1998 cohort had -2.86 (95% CI: [-3.17, -2.55]) increased log odds) compared with the mean across years. Results were consistent by sex and varied by education. We observed a negative period effect for criminalization favorability (0.14 (95% CI: [0.003, 0.28]) increased log odds in 2001 vs. -0.31 (95% CI: [-0.45, -0.17]) increased log odds in 2016) and positive cohort effect for recent cohorts. Last, we observed a positive period effect for legalization support (-0.03 (95% CI: [-0.20, 0.14]) increased log odds in 2001 vs. 0.38 (95% CI: [0.22, 0.55]) increased log odds in 2016) and negative cohort effect for recent cohorts. CONCLUSION: Cannabis use appears to be increasing in Australia among adults over 35, while decreasing among adolescents and young adults. Legalization support also appears to have been increasing since 2007, signaling discordance between use and attitudes among adolescents and young adults, and potentially predicting increases in use over time.

DSM-5 and ICD-11 alcohol use disorder criteria in young adult regular drinkers: Lifetime prevalence and age of onset.

BACKGROUND: Alcohol Use Disorder (AUD) is a significant contributor to global disease burden. AUD has a relatively early onset during young adulthood (Teesson et al., 2010). However, compared to AUD in adults, we have relatively little understanding of AUD in adolescents and emerging adults. METHODS: The RADAR study is a prospective cohort study designed to investigate the emergence of AUD in community-dwelling adolescents and emerging adults across Australia (age range = 18-21 at baseline). At 6 monthly intervals over 2.5 years, participants were interviewed regarding alcohol consumption and alcohol use disorder criteria by clinical psychologists using the SCID-IV-RV. This paper reports the baseline findings of the RADAR cohort. RESULTS: Proportions of lifetime criteria endorsement among regular drinkers varied considerably. Tolerance was the most endorsed criterion (50.3%), followed by Social Problems (10.4%) and Larger/Longer (9.0%). The median age of onset for most individual AUD criteria was 18 years of age. 18.4% of our cohort met DSM-5 AUD diagnosis in their lifetime to date, and 16.8% met ICD-11 dependence. When removing Tolerance from the AUD criteria, DSM-5 AUD lifetime prevalence reduced to 11.0%, and ICD-11 AUD lifetime prevalence fell to 7.1% in our cohort. CONCLUSIONS: Variable rates of criteria endorsement likely reflect both true differences in the experience of AUD criteria and methodological challenges in the assessment of AUD in an emerging adult age group. High rates of tolerance to the effects of alcohol, and relatively low rates of drinking larger/longer than intended are discussed considering methodological challenges in assessing these criteria in young adults.

Outcomes of occasional cannabis use in adolescence: 10-year follow-up study in Victoria, Australia.

BACKGROUND: Regular adolescent cannabis use predicts a range of later drug use and psychosocial problems. Little is known about whether occasional cannabis use carries similar risks. AIMS: To examine associations between occasional cannabis use during adolescence and psychosocial and drug use outcomes in young adulthood; and modification of these associations according to the trajectory of cannabis use between adolescence and age 20 years, and other potential risk factors. METHOD: A 10-year eight-wave cohort study of a representative sample of 1943 secondary school students followed from 14.9 years to 24 years. RESULTS: Occasional adolescent cannabis users who continued occasional use into early adulthood had higher risks of later alcohol and tobacco dependence and illicit drug use, as well as being less likely to complete a post-secondary qualification than non-users. Those using cannabis at least weekly either during adolescence or at age 20 were at highest risk of drug use problems in young adulthood. Adjustment for smoking in adolescence reduced the association with later educational achievement, but associations with drug use problems remained. CONCLUSIONS: Occasional adolescent cannabis use predicts later drug use and educational problems. Partial mediation by tobacco use raises a possibility that differential peer affiliation may play a role.

Elite athletes' perceptions of the effects of illicit drug use on athletic performance.

OBJECTIVE: To investigate the perceived risks and benefits that elite athletes associate with illicit drugs and their beliefs concerning the effects of recreational drug use on athletic performance. DESIGN: Self-administered survey. PARTICIPANTS: Nine hundred seventy-four elite athletes (mean age, 23 years; range, 18-30 years) were recruited from 8 national sporting organizations in Australia and the Australian Institute of Sport. INTERVENTIONS: Participants completed a self-administered survey that included questions exploring participants' perceptions regarding the effects of illicit drug use on physical performance. SETTING: National sporting organization meetings or competitions. MAIN OUTCOME MEASURES: The main outcome measure was risk perception on athletic performance associated with illicit drug use. RESULTS: The majority of athletes believed that illicit drug use would impact negatively on athletic performance. The main perceived effects of illicit drugs on athletic performance were physical and mental functioning. A minority of athletes indicated that drug use would not impact on physical performance when taken during the off-season or in moderation. CONCLUSIONS: The main risks perceived in association with illicit drug use were short-term consequences, such as physical and mental functioning, rather than long-term health consequences. The current findings may contribute to the development of harm reduction strategies that communicate drug-related consequences to elite athletes in an appropriate and effective manner.

Cannabis use disorder: epidemiology and management.

This paper provides an overview of the epidemiology of cannabis use, cannabis use disorders and its treatment. Cannabis is the most commonly used illicit drug internationally. While use is decreasing in the developed world, it appears to be stable or increasing in developing countries and some indigenous communities. Early initiation and regular adolescent use have been identified as particular risk factors for later problematic cannabis (and other drug) use, impaired mental health, delinquency, lower educational achievement, risky sexual behaviour and criminal offending in a range of studies. It is estimated that approximately one in ten people who had ever used cannabis will become dependent with risk increasing markedly with frequency of use. There has been an increase in the proportion of treatment provided for cannabis use. There are as yet no evidence-based pharmacotherapies available for the management of cannabis withdrawal and craving. Relatively brief cognitive behavioural therapy and contingency management have the strongest evidence of success, and structured, family-based interventions, provide potent treatment options for adolescents. With criminally involved young people and those with severe, persistent mental illness, longer and more intensive therapies provided by interdisciplinary teams may be required.

Cannabis potency and contamination: a review of the literature.

AIMS: Increased potency and contamination of cannabis have been linked in the public domain to adverse mental health outcomes. This paper reviews the available international evidence on patterns of cannabis potency and contamination and potential associated harms, and discusses their implications for prevention and harm reduction measures. METHODS: A systematic literature search on cannabis potency and contamination was conducted. RESULTS: Cannabis samples tested in the United States, the Netherlands, United Kingdom and Italy have shown increases in potency over the last 10 years. Some countries have not shown significant increases in potency, while other countries have not monitored potency over time. While there are some grounds to be concerned about potential contaminants in cannabis, there has been no systematic monitoring. CONCLUSION: Increased potency has been observed in some countries, but there is enormous variation between samples, meaning that cannabis users may be exposed to greater variation in a single year than over years or decades. Claims made in the public domain about a 20- or 30-fold increase in cannabis potency and about the adverse mental health effects of cannabis contamination are not supported currently by the evidence. Systematic scientific testing of cannabis is needed to monitor current and ongoing trends in cannabis potency, and to determine whether cannabis is contaminated. Additionally, more research is needed to determine whether increased potency and contamination translates to harm for users, who need to be provided with accurate and credible information to prevent and reduce harms associated with cannabis use.

Adolescent cannabis users at 24 years: trajectories to regular weekly use and dependence in young adulthood.

AIMS: To examine the association between cannabis use by 18 years and problematic cannabis use at 24 years, considering possible mediating and confounding factors. DESIGN: Ten-year representative prospective study with data from six time-points in adolescence (mean age 14.9-17.4 years) and two in young adulthood (mean age 20.7 and 24.1 years) SETTING: Victoria, Australia. PARTICIPANTS: Inception cohort of 1943 secondary school students (95.6% response rate), with 1520 (78% of adolescent participants) interviewed in the final wave. MEASUREMENTS: Participants reported frequency of cannabis use for the past 6 months at each time-point in adolescence (age 14-17 years). Cannabis exposure was defined as: maximum frequency of use (occasional, weekly, daily), number of waves of use (1 or 2; 3-6) and first wave of use (early use: first waves 1-3). Young adult (24 years) outcomes were: weekly+ cannabis use and DSM-IV cannabis dependence, referred to collectively as problematic use. FINDINGS: Of those interviewed at age 24 (wave 8), 34% had reported cannabis use in adolescence (waves 1-6), 12% at a level of weekly or more frequent use; 37% of these adolescent cannabis users were using at least weekly at wave 8, with 20% exhibiting dependence. Persistent adolescent cannabis and tobacco use as well as persistent mental health problems were associated strongly with problematic cannabis use at 24 years, after adjustment for potential confounding factors. CONCLUSIONS: Heavy, persistent and early-onset cannabis use were all strongly predictive of later cannabis problems. Even so, occasional use was not free of later problems. Where there was co-occurring tobacco use or persistent mental health problems, risks for later problem cannabis use was higher.

Are diagnostic orphans at risk of developing cannabis abuse or dependence? Four-year follow-up of young adult cannabis users not meeting diagnostic criteria.

OBJECTIVE: To examine the characteristics of "diagnostic orphans" among cannabis users - those who report one or two symptoms of DSM-IV dependence but do not meet diagnostic criteria for DSM-IV abuse or dependence - 4 years post-assessment. METHOD: Data were collected from a representative population cohort of young Australian adults. Those who reported that they had used cannabis at least weekly at some point within the past year were assessed for symptoms of DSM-IV cannabis abuse and dependence using the Composite International Diagnostic Interview at age 20-21 years. The entire sample was followed up 4 years later. At age 24-25 years, cannabis use and cannabis diagnostic category were examined according to diagnostic category at age 20-21 years. RESULTS: Diagnostic orphans at age 20-21 years were more likely than non-problem cannabis users at that age to be using cannabis, and to meet criteria for cannabis abuse or dependence 4 years later. Those who had met criteria for cannabis abuse or dependence, however, appeared to be at greater risk relative to non-problematic users and diagnostic orphans of meeting criteria for cannabis abuse and dependence at follow-up. CONCLUSIONS: Young adult diagnostic orphans for cannabis use appear to be at lower risk of meeting full (or partial) diagnostic criteria after a 4-year follow-up, compared to those who had met criteria for cannabis abuse or dependence. This suggests that there is prognostic diagnostic utility in the threshold for dependence symptoms among young adult cannabis users. Diagnostic orphans did appear to be at greater risk than non-problem users for developing dependent and daily cannabis use, however, suggesting that clinicians would do well to intervene with this group.

Correlates of driving under the influence of cannabis.

BACKGROUND: Identifying cannabis users who are most at risk of driving under the influence of cannabis (DUIC) has important implications for drug treatment and prevention efforts. This paper examined correlates of DUIC among a purposive sample of recent cannabis users. METHODS: Interviews were carried out among a cross-sectional sample of 320 Australian cannabis users. Past-year prevalence of DUIC (without using alcohol or other drugs) was regressed against a range of potential predictor variables. RESULTS: Use of multiple drugs, believing that DUIC does not increase accident risk and cannabis dependence all predicted likelihood of DUIC. There was an interaction between age of first cannabis use and gender, whereby earlier onset cannabis use predicted DUIC but only among women. CONCLUSIONS: The correlates of drug driving reflected cannabis users' beliefs about the dangers of cannabis use as well as their patterns of drug consumption. The emergence of cannabis dependence and age of onset as predictors of DUIC suggests a clearly defined role for treatment and prevention efforts in reducing the potential harms associated with DUIC.

The use of alcohol and medicines among Australian adults.

OBJECTIVE: To collect Australian population-based data on concurrent use of conventional medicines, complementary/alternative medicines (CAM), and alcohol. METHOD: National survey administered in December 2005 to 816 Australian adults. RESULTS: 71% of respondents reported recent (last 24 hour) use of conventional medicine or CAM. 24% had recently consumed alcohol and conventional medicine, 17% alcohol and CAM and 13% alcohol and both types of medicines. Use of blood pressure and arthritis medicines was significantly more likely among daily drinkers than less than daily drinkers and non-drinkers. CONCLUSIONS: Concurrent use of medicines and alcohol is common, particularly among older people. IMPLICATIONS: Use of alcohol may have an impact on the stability of chronic illness managed by medicines or other types of interactions with medicines, such as sedation. Health care professionals should routinely inquire about such use to be able to incorporate appropriate safety strategies into clinical management.

Evidence for Sex Convergence in Prevalence of Cannabis Use: A Systematic Review and Meta-Regression.

OBJECTIVE: Generally, cannabis use has been more prevalent in men than in women. However, emerging evidence suggests that the prevalence of cannabis use is converging among males and females from recent cohorts. This study aimed to systematically summarize published literature on birth cohort changes in male-to-female ratios in prevalence of cannabis use. METHOD: Twenty-two studies with a median sample size of 85,052 were identified for inclusion. Data were collected between 1979 and 2010, representing birth cohorts from 1936 to 1999. For quantitative synthesis, male-to-female ratios in prevalence of any cannabis use were calculated for all 5-year birth cohorts available, generating 348 separate ratios among birth cohorts from 1941 to 1995 in 30 countries. Random-effects meta-analyses generated pooled sex ratios, stratified by 5-year birth cohorts. RESULTS: Of the 22 included studies, 10 reported some evidence of sex convergence in cannabis use among more recent cohorts. Quantitative synthesis found that the ratio of cannabis use prevalence in males and females decreased significantly from 2.0 among cohorts born in 1941 to 1.3 among those born in 1995. CONCLUSIONS: Findings support the narrowing sex gap in the prevalence of cannabis use. Results are concordant with a broader literature demonstrating sex convergence in prevalence of other substance use, particularly alcohol use and related harms. Both young women and men should be the target of prevention and early intervention efforts. Future research in more diverse global settings, especially in low- and middle-income countries, would enhance the international scope of the findings.

First examination of varying health outcomes of the chronically homeless according to Housing First configuration.

OBJECTIVE: To determine whether two Housing First configurations (scattered site [SS] versus congregated site [CS]) are associated with different health-related outcomes. METHODS: This ecological study employed a longitudinal, quantitative design to compare the outcomes from 63 individuals (SS: n=37; CS: n=26) in Sydney, Australia, over 12 months. RESULTS: Both configurations showed similar improvements in quality of life and psychological distress. While recent use of substances remained stable across the two configurations over time, a marginally greater increase in the proportion of CS individuals injecting more than weekly was found. For health service utilisation, CS participants had notably higher service utilisation rates for mental health specialists and the emergency department for mental health reasons at follow-up than SS participants. CONCLUSION: Preliminary evidence of differential injecting and health service utilisation outcomes between configurations emerged within this small-scale study over the 12-month period. Implications for public health: Given the rapid expansion of both SS and CS Housing First configurations across Western countries and the indications from this initial study that outcomes may differ according to configuration, there remains a need for robust evaluative evidence on the efficacy of various supported housing models on long-term individual outcomes.

A prospective study of the substance use and mental health outcomes of young adult former and current cannabis users.

INTRODUCTION AND AIMS: The extent to which young adult former cannabis users fare better than infrequent users is unclear. We investigated the association between cannabis use status at age 23 and substance use and mental health outcomes at age 27. DESIGN AND METHODS: Data were from the 20+ year cohort of the PATH Through Life Study. Lifetime cannabis users (n = 1410) at age 23 were classified as former/occasional/regular users. Multivariable logistic regression was used to estimate the association between cannabis use status at age 23 and six outcomes assessed at age 27. RESULTS: Compared with occasional cannabis users: (i) former users had odds of subsequent tobacco use [odds ratio (OR) = 0.67, 95% confidence interval (CI) 0.52-0.85], illicit drug use (cannabis, OR = 0.22, 95% CI 0.17-0.28; other illicit drugs, OR = 0.29, 95% CI 0.22-0.39) and mental health impairment (OR = 0.71, 95% CI 0.55-0.92) that were 29-78% lower; and (ii) regular users had odds of subsequent frequent alcohol use (OR = 2.34, 95% CI 0.67-1.34), tobacco use (OR = 3.67, 95% CI 2.54-5.30), cannabis use (OR = 11.73, 95% CI 6.81-20.21) and dependence symptoms (OR = 12.60, 95% CI 8.38-18.94), and other illicit drug use (OR = 2.95, 95% CI 2.07-4.21) that were 2-13 times greater. Associations attenuated after covariate adjustment, and most remained significant. DISCUSSION AND CONCLUSIONS: Clear associations exist between cannabis use status in young adulthood and subsequent mental health and substance use. While early intervention remains important to prevent regular cannabis use and the associated harms, experimentation with cannabis use in the years leading into young adulthood may not necessarily determine an immutable pathway to mental health problems and illicit substance use. [Silins E, Swift W, Slade T, Toson B, Rodgers B, Hutchinson DM. A prospective study of the substance use and mental health outcomes of young adult former and current cannabis users. Drug Alcohol Rev 2017;00:000-000].

RADAR study: protocol for an observational cohort study to identify early warning signals on the pathways to alcohol use disorder.

INTRODUCTION: Harmful alcohol consumption, particularly alcohol use disorder (AUD), is a worldwide health priority, contributing substantially to global morbidity and mortality. The peak age of onset of AUD is 18-24, thus a deeper understanding of the young adult experience is vital if we are to identify modifiable risk factors and intervene early in the developmental course of this disabling disorder. Critical unanswered questions include: How soon after drinking initiation do AUD symptoms begin to emerge? Which symptoms come first? Do the symptoms unfold in a predictable pattern? In what ways do the emerging symptoms interact with individual, peer, family and environmental risk factors to impact on the transition to disorder? METHODS AND ANALYSIS: The proposed RADAR study will examine the prospective development of AUD symptoms over the young adulthood (18-24) years. We will capitalise on an existing cohort of 1911 community-based adolescents who were recruited at age 13 and have completed a baseline and five annual follow-up assessments as part of an observational cohort study. We will interview these adolescents every 6 months between the ages of 19 and 23 to derive monthly histories of both alcohol use and AUD symptomatology, along with a comprehensive battery of risk and protective factor scales hypothesised to predict the emergence and course of AUD. The results of this study will inform the natural history of AUD and will be used to identify specific targets for prevention and early intervention of AUD. ETHICS AND DISSEMINATION: Ethical approval has already been granted for the study (UNSW HREC 10144). We will disseminate the results of the study through published manuscripts, conferences and seminar presentations. Data used in published manuscripts will be made available through a suitable online repository (eg, Dryad-datadryad.org).