Young-adult compared to adolescent onset of regular cannabis use: A 20-year prospective cohort study of later consequences.

INTRODUCTION: This paper compares consequences of cannabis use initiated after high school with those of cannabis initiation in adolescence, with estimates of the proportion of adverse consequences accounted for by adult-onset and adolescent-onset cannabis users. METHODS: A state-representative sample in Victoria, Australia (n = 1792) participated in a 10-wave longitudinal study and was followed from age 15 to 35 years. Exposure variable: Patterns of cannabis use across 20 years. Outcomes at age 35: Alcohol use, smoking, illicit drug use, relationship status, financial hardship, depression, anxiety and employment status. RESULTS: Substantially more participants (13.6%) initiated regular use after high school (young-adult onset) than in adolescence (7.7%, adolescent onset). By the mid-30s, both young-adult and adolescent-onset regular users were more likely than minimal/non-users (63.5%) to have used other illicit drugs (odds ratio [OR] > 20.4), be a high-risk alcohol drinker (OR > 3.7), smoked daily (OR > 7.2) and less likely to be in relationships (OR < 0.4). As the prevalence of the young-adult-onset group was nearly double of the adolescent-onset group, it accounted for a higher proportion of adverse consequences than the adolescent-onset group. DISCUSSION AND CONCLUSIONS: Cannabis users who began regular use in their teens had poorer later life outcomes than non-using peers. The larger group who began regular cannabis use after leaving high school accounted for most cannabis-related harms in adulthood. Given the legalisation of cannabis use in an increasing number of jurisdictions, we should increasingly expect harms from cannabis use to lie in those commencing use in young adulthood.

The Victorian Intergenerational Health Cohort Study (VIHCS): Study design of a preconception cohort from parent adolescence to offspring childhood.

BACKGROUND: There is increasing evidence that parental determinants of offspring early life development begin well before pregnancy. OBJECTIVES: We established the Victorian Intergenerational Health Cohort Study (VIHCS) to examine the contributions of parental mental health, substance use, and socio-economic characteristics before pregnancy to child emotional, physical, social, and cognitive development. POPULATION: Men and women were recruited from the Victorian Adolescent Health Cohort (VAHCS), an existing cohort study beginning in 1992 that assessed a representative sample of 1943 secondary school students in Victoria, Australia, repeatedly from adolescence (wave 1, mean age 14 years) to adulthood (wave 10, mean age 35 years). METHODS: Victorian Adolescent Health Cohort participants with children born between 2006 and 2013 were recruited to VIHCS and invited to participate during trimester three, at 2 months postpartum, and 1 year postpartum. Parental mental health, substance use and socio-economic characteristics were assessed repeatedly throughout; infant characteristics were assessed postnatally and in infancy. Data will be supplemented by linkage to routine datasets. A further follow-up is underway as children reach 8 years of age. PRELIMINARY RESULTS: Of the 1307 infants born to VAHCS participants between 2006 and 2013, 1030 were recruited to VIHCS. At VIHCS study entry, 18% of recruited parents had preconception common mental disorder in adolescence and young adulthood, 18% smoked daily in adolescence and young adulthood, and 6% had not completed high school. Half of VIHCS infants were female (48%), 4% were from multiple births, and 7% were preterm (<37 weeks' gestation). CONCLUSIONS: Victorian Intergenerational Health Cohort Study is a prospective cohort of 1030 children with up to nine waves of preconception parental data and three waves of perinatal parental and infant data. These will allow examination of continuities of parental health and health risks from the decades before pregnancy to offspring childhood, and the contributions of exposures before pregnancy to offspring outcomes in childhood.

20-year outcomes in adolescents who self-harm: a population-based cohort study.

BACKGROUND: Little is known about the long-term psychosocial outcomes associated with self-harm during adolescence. We aimed to determine whether adolescents who self-harm are at increased risk of adverse psychosocial outcomes in the fourth decade of life, using data from the Victorian Adolescent Health Cohort Study. METHODS: We recruited a stratified, random sample of 1943 adolescents from 44 schools across the state of Victoria, Australia. The study started on Aug 20, 1992, and finished on March 4, 2014. We obtained data relating to self-harm from questionnaires and telephone interviews at eight waves of follow-up, commencing at mean age 15·9 years (SD 0·5; waves 3-6 during adolescence, 6 months apart) and ending at mean age 35·1 years (SD 0·6; wave 10). The outcome measures at age 35 years were social disadvantage (divorced or separated, not in a relationship, not earning money, receipt of government welfare, and experiencing financial hardship), common mental disorders such as depression and anxiety, and substance use. We assessed the associations between self-harm during adolescence and the outcome measures at 35 years (wave 10) using logistic regression models, with progressive adjustment: (1) adjustment for sex and age; (2) further adjustment for background social factors; (3) additional adjustment for common mental disorder in adolescence; and (4) final additional adjustment for adolescent antisocial behaviour and substance use measures. FINDINGS: From the total cohort of 1943 participants, 1802 participants were assessed for self-harm during adolescence (between waves 3 and 6). Of these, 1671 were included in the analysis sample. 135 (8%) reported having self-harmed at least once during adolescence. At 35 years (wave 10), mental health problems, daily tobacco smoking, illicit drug use, and dependence were all more common in participants who had reported self-harm during the adolescent phase of the study (n=135) than in those who had not (n=1536): for social disadvantage odds ratios [ORs] ranged from 1·34 (95% CI 1·25-1·43) for unemployment to 1·88 (1·78-1·98) for financial hardship; for mental health they ranged from 1·61 (1·51-1·72) for depression to 1·92 (1·79-2·04) for anxiety; for illicit drug use they ranged from 1·36 (1·25-1·49) for any amphetamine use to 3·39 (3·12-3·67) for weekly cannabis use; for dependence syndrome they were 1·72 (1·57-1·87) for nicotine dependence, 2·67 (2·38-2·99) for cannabis dependence, and 1·74 (1·62-1·86) for any dependence; and the OR for daily smoking was 2·00 (1·89-2·12). Adjustment for socio-demographic factors made little difference to these associations but a further adjustment for adolescent common mental disorders substantially attenuated most associations, with the exception of daily tobacco smoking (adjusted OR 1·74, 95% CI 1·08-2·81), any illicit drug use (1·72, 1·07-2·79) and weekly cannabis use (3·18, 1·58-6·42). Further adjustment for adolescent risky substance use and antisocial behaviour attenuated the remaining associations, with the exception of weekly cannabis use at age 35 years, which remained independently associated with self-harm during adolescence (2·27, 1·09-4·69). INTERPRETATION: Adolescents who self-harm are more likely to experience a wide range of psychosocial problems later in life. With the notable exception of heavy cannabis use, these problems appear to be largely accounted for by concurrent adolescent mental health disorders and substance use. Complex interventions addressing the domains of mental state, behaviour, and substance use are likely to be most successful in helping this susceptible group adjust to adult life. FUNDING: National Health and Medical Research Council, the Royal Children's Hospital Foundation, and the Murdoch Childrens Research Institute.

Adolescent Predictors of a Typology of DSM-5 Alcohol Use Disorder Symptoms in Young Adults Derived by Latent Class Analysis Using Data From an Australian Cohort Study.

OBJECTIVE: There is little research examining alcohol use disorder (AUD) symptoms (based on criteria from the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition [DSM-5]) in young adulthood. We assessed symptom structure at 24 years using latent class analysis (LCA), examining relationships between class membership and (a) concurrent alcohol use and DSM-5 AUD severity and (b) adolescent risk factors. METHOD: A stratified, random sample of 1,943 adolescents ages 14-15 years was recruited from 44 secondary schools in Victoria, Australia, and interviewed during adolescence and young adulthood. We report findings on drinkers who completed the AUD module (N = 1,268; 51% male). RESULTS: Data clearly fit a three-class, dimensional model, comprising "mild symptoms" (63.2%), "moderate symptoms" (32.2%), and "severe symptoms" (4.6%) classes. Class membership was validated by concurrent drinking patterns and in reasonable agreement with DSM-5 AUD severity categories. Relative to mild symptoms class membership, moderate symptoms class membership increased odds of adolescent alcohol problems (odds ratio [OR] = 2.0, 95% CI [1.2, 3.5]) and persisting anxiety/depression symptoms (OR = 1.9, 95% CI [1.2, 3.1]). Daily smoking (OR = 2.6, 95% CI [1.1, 5.9]), persisting anxiety/ depression symptoms (OR = 2.5, 95% CI [1.3, 5.0]), and antisocial behavior (OR = 3.2, 95% CI [1.5, 6.8]) increased odds of severe symptoms class membership. Adolescent daily smoking (OR = 0.3, 95% CI [0.11, 0.81]) and antisocial behavior (OR = 0.3, 95% CI [0.14, 0.64]) were less likely among members of the moderate symptoms class, relative to the severe symptoms class. CONCLUSIONS: We found support for a dimensional AUD typology like that in DSM-5. Young adults with more severe AUD symptoms had a different adolescent risk profile than those in the low and moderate classes. These findings provide a focus for preventive intervention in adolescence to limit the severity of AUDs in young adulthood.

The influence of personality disorder on the future mental health and social adjustment of young adults: a population-based, longitudinal cohort study.

BACKGROUND: Existing knowledge about the consequences of personality disorders is substantially derived from the study of clinical populations. To gain a fuller understanding of the disease burden associated with personality disorders, we report their long-term mental health and social consequences in a large population-based sample of young adults. METHODS: We used data from a population-based, ten-wave cohort study of a stratified random sample of non-treatment-seeking young adults recruited from Victoria, Australia, between Aug 20, 1992, and March 3, 2014. The population sample was originally recruited in adolescence: here we report the analysis of data collected from wave 8 (participants aged 24-25 years) and wave 10 (participants aged 34-35 years). Presence and severity of personality disorder were assessed at age 24 years with a semi-structured, informant-based interview (the Standardised Assessment of Personality). At age 35 years, participants were assessed on the occurrence of the following outcomes: major depressive disorder, anxiety disorder, smoking and alcohol consumption, illicit substance use, ever having separated from a long-term partner or been divorced, not currently in a relationship, not currently in paid employment, and in receipt of government welfare. We used multiple imputation to address potentially biased estimates resulting from the reduction of the analysis sample to participants who had completed both survey waves. The imputation dataset contained 1635 individuals. FINDINGS: For the 1520 participants in wave 8, 1145 (75%) informant interviews for personality disorder in these participants took place. At age 24 years, 305 (27%) of the observed sample had either personality difficulties or personality disorder. At age 24 years, in the imputed analysis sample, the severity of personality disorder was associated with the absence of a degree or vocational qualification (adjusted odds ratio [aOR] for the effect of complex and severe personality disorder vs no personality disorder 1·76, 95% CI 1·11-2·76), receipt of welfare (2·52, 1·33-4·78), the presence of common mental disorders (1·77, 1·08-2·90), and cigarette smoking (2·01, 1·29-3·14). At age 35 years, severity of personality disorder was independently associated with not being in a relationship (aOR for the effect of complex and severe personality disorder vs no personality disorder or personality difficulty 2·05, 95% CI 1·21-3·45), increased odds of an anxiety disorder (2·27, 1·2-4·28), and major depression (2·23, 1·24-4·01). INTERPRETATION: The presence of personality disorder predicts the occurrence of later anxiety and depression, as well as the absence of long-term relationships, effects that are not attributable to pre-existing mental health, substance use or social problems. Our study provides strong support for including personality disorder in global studies of the burden of mental disorders to improve the understanding of population mental health. FUNDING: Australia's National Health and Medical Research Council (NHMRC) and Victoria's Operational Infrastructure Support Program.

Adolescent substance use and educational attainment: An integrative data analysis comparing cannabis and alcohol from three Australasian cohorts.

BACKGROUND: The relative contributions of cannabis and alcohol use to educational outcomes are unclear. We examined the extent to which adolescent cannabis or alcohol use predicts educational attainment in emerging adulthood. METHODS: Participant-level data were integrated from three longitudinal studies from Australia and New Zealand (Australian Temperament Project, Christchurch Health and Development Study, and Victorian Adolescent Health Cohort Study). The number of participants varied by analysis (N=2179-3678) and were assessed on multiple occasions between ages 13 and 25. We described the association between frequency of cannabis or alcohol use prior to age 17 and high school non-completion, university non-enrolment, and degree non-attainment by age 25. Two other measures of alcohol use in adolescence were also examined. RESULTS: After covariate adjustment using a propensity score approach, adolescent cannabis use (weekly+) was associated with 1½ to two-fold increases in the odds of high school non-completion (OR=1.60, 95% CI=1.09-2.35), university non-enrolment (OR=1.51, 95% CI=1.06-2.13), and degree non-attainment (OR=1.96, 95% CI=1.36-2.81). In contrast, adjusted associations for all measures of adolescent alcohol use were inconsistent and weaker. Attributable risk estimates indicated adolescent cannabis use accounted for a greater proportion of the overall rate of non-progression with formal education than adolescent alcohol use. CONCLUSIONS: Findings are important to the debate about the relative harms of cannabis and alcohol use. Adolescent cannabis use is a better marker of lower educational attainment than adolescent alcohol use and identifies an important target population for preventive intervention.

The persistence of the association between adolescent cannabis use and common mental disorders into young adulthood.

AIMS: Debate continues about whether the association between cannabis use in adolescence and common mental disorders is causal. Most reports have focused on associations in adolescence, with few studies extending into adulthood. We examine the association from adolescence until the age of 29 years in a representative prospective cohort of young Australians. DESIGN: Nine-wave, 15-year representative longitudinal cohort study, with six waves of data collection in adolescence (mean age 14.9-17.4 years) and three in young adulthood (mean age 20.7, 24.1 and 29.1 years). PARTICIPANTS: Participants were a cohort of 1943 recruited in secondary school and surveyed at each wave when possible from mid-teen age to their late 20s. SETTING: Victoria, Australia. MEASUREMENTS: Psychiatric morbidity was assessed with the Revised Clinical Interview Schedule (CIS-R) at each adolescent wave, and as Composite International Diagnostic Interview (CIDI)-defined ICD-10 major depressive episode and anxiety disorder at 29 years. Frequency of cannabis use was measured in the past 6 months in adolescence. Cannabis use frequency in the last year and DSM-IV cannabis dependence were assessed at 29 years. Cross-sectional and prospective associations of these outcomes with cannabis use and dependence were estimated as odds ratios (OR), using multivariable logistic regression models, with the outcomes of interest, major depressive episode (MDE) and anxiety disorder (AD) at 29 years. FINDINGS: There were no consistent associations between adolescent cannabis use and depression at age 29 years. Daily cannabis use was associated with anxiety disorder at 29 years [adjusted OR 2.5, 95% confidence interval (CI):< 1.2-5.2], as was cannabis dependence (adjusted OR 2.2, 95% CI: 1.1-4.4). Among weekly+ adolescent cannabis users, those who continued to use cannabis use daily at 29 years remained at significantly increased odds of anxiety disorder (adjusted OR 3.2, 95% CI: 1.1-9.2). CONCLUSIONS: Regular (particularly daily) adolescent cannabis use is associated consistently with anxiety, but not depressive disorder, in adolescence and late young adulthood, even among regular users who then cease using the drug. It is possible that early cannabis exposure causes enduring mental health risks in the general cannabis-using adolescent population.

Health of the world's adolescents: a synthesis of internationally comparable data.

Adolescence and young adulthood offer opportunities for health gains both through prevention and early clinical intervention. Yet development of health information systems to support this work has been weak and so far lagged behind those for early childhood and adulthood. With falls in the number of deaths in earlier childhood in many countries and a shifting emphasis to non-communicable disease risks, injuries, and mental health, there are good reasons to assess the present sources of health information for young people. We derive indicators from the conceptual framework for the Series on adolescent health and assess the available data to describe them. We selected indicators for their public health importance and their coverage of major health outcomes in young people, health risk behaviours and states, risk and protective factors, social role transitions relevant to health, and health service inputs. We then specify definitions that maximise international comparability. Even with this optimisation of data usage, only seven of the 25 indicators, covered at least 50% of the world's adolescents. The worst adolescent health profiles are in sub-Saharan Africa, with persisting high mortality from maternal and infectious causes. Risks for non-communicable diseases are spreading rapidly, with the highest rates of tobacco use and overweight, and lowest rates of physical activity, predominantly in adolescents living in low-income and middle-income countries. Even for present global health agendas, such as HIV infection and maternal mortality, data sources are incomplete for adolescents. We propose a series of steps that include better coordination and use of data collected across countries, greater harmonisation of school-based surveys, further development of strategies for socially marginalised youth, targeted research into the validity and use of these health indicators, advocating for adolescent-health information within new global health initiatives, and a recommendation that every country produce a regular report on the health of its adolescents.

Cannabis and progression to other substance use in young adults: findings from a 13-year prospective population-based study.

BACKGROUND: Adolescent cannabis use predicts the onset of later illicit drug use. In contrast, little is known about whether cannabis in young adulthood also predicts subsequent progression or cessation of licit or illicit drug use. METHODS: 13-year longitudinal cohort study with recruitment in secondary school students in Victoria, Australia. There were six waves of adolescent data collection (mean age 14.9-17.4 years) followed by three in young adulthood (mean age 20.7, 24.1 and 29.0 years). Discrete-time proportional hazards models were used to assess predictive associations between cannabis use frequency (occasional (

The natural history of self-harm from adolescence to young adulthood: a population-based cohort study.

BACKGROUND: Knowledge about the natural history of self-harm is scarce, especially during the transition from adolescence to young adulthood, a period characterised by a sharp rise in self-inflicted deaths. From a repeated measures cohort of a representative sample, we describe the course of self-harm from middle adolescence to young adulthood. METHODS: A stratified, random sample of 1943 adolescents was recruited from 44 schools across the state of Victoria, Australia, between August, 1992, and January, 2008. We obtained data pertaining to self-harm from questionnaires and telephone interviews at seven waves of follow-up, commencing at mean age 15·9 years (SD 0·49) and ending at mean age 29·0 years (SD 0·59). Summary adolescent measures (waves three to six) were obtained for cannabis use, cigarette smoking, high-risk alcohol use, depression and anxiety, antisocial behaviour and parental separation or divorce. FINDINGS: 1802 participants responded in the adolescent phase, with 149 (8%) reporting self-harm, More girls (95/947 [10%]) than boys (54/855 [6%]) reported self-harm (risk ratio 1·6, 95% CI 1·2-2·2). We recorded a substantial reduction in the frequency of self-harm during late adolescence. 122 of 1652 (7%) participants who reported self-harm during adolescence reported no further self-harm in young adulthood, with a stronger continuity in girls (13/888) than boys (1/764). During adolescence, incident self-harm was independently associated with symptoms of depression and anxiety (HR 3·7, 95% CI 2·4-5·9), antisocial behaviour (1·9, 1·1-3·4), high-risk alcohol use (2·1, 1·2-3·7), cannabis use (2·4, 1·4-4·4), and cigarette smoking (1·8, 1·0-3·1). Adolescent symptoms of depression and anxiety were clearly associated with incident self-harm in young adulthood (5·9, 2·2-16). INTERPRETATION: Most self-harming behaviour in adolescents resolves spontaneously. The early detection and treatment of common mental disorders during adolescence might constitute an important and hitherto unrecognised component of suicide prevention in young adults. FUNDING: National Health and Medical Research Council, Australia, and operational infrastructure support programme, Government of Victoria, Australia.

Cannabis use and educational achievement: findings from three Australasian cohort studies.

BACKGROUND: The associations between age of onset of cannabis use and educational achievement were examined using data from three Australasian cohort studies involving over 6000 participants. The research aims were to compare findings across studies and obtain pooled estimates of association using meta-analytic methods. METHODS: Data on age of onset of cannabis use (<15, 15-17, never before age 18) and three educational outcomes (high school completion, university enrolment, degree attainment) were common to all studies. Each study also assessed a broad range of confounding factors. RESULTS: There were significant (p<.001) associations between age of onset of cannabis use and all outcomes such that rates of attainment were highest for those who had not used cannabis by age 18 and lowest for those who first used cannabis before age 15. These findings were evident for each study and for the pooled data, and persisted after control for confounding. There was no consistent trend for cannabis use to have greater effect on the academic achievement of males but there was a significant gender by age of onset interaction for university enrolment. This interaction suggested that cannabis use by males had a greater detrimental effect on university participation than for females. Pooled estimates suggested that early use of cannabis may contribute up to 17% of the rate of failure to obtain the educational milestones of high school completion, university enrolment and degree attainment. CONCLUSIONS: Findings suggest the presence of a robust association between age of onset of cannabis use and subsequent educational achievement.

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.

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.

Problem alcohol use in young Australian adults.

OBJECTIVE: To examine the extent to which excessive drinking in young adults is associated with alcohol abuse and dependence. METHOD: Cross-sectional analyses were conducted using data from the eighth wave of the Victorian Adolescent Health Cohort Study, which comprised 1943 Victorians currently aged 24-25 years drawn from 44 secondary schools across the state in 1992. The main outcome measures of interest were short-term risk drinking status (based on daily alcohol consumption) and long-term risk drinking status (based on total weekly alcohol consumption). RESULTS: Two out of 5 participants drank at moderate to high risk levels for short-term harm. Yet, because young people tend to drink on only 1-2 days a week, fewer (22%) were at moderate to high risk for long-term harm. Although 20% of the participants met criteria for a diagnosis of alcohol abuse or dependence, most of those in the moderate- to high-risk drinking categories were not diagnosed with either alcohol disorder. CONCLUSION: Excessive alcohol use in one or two sessions a week appears to be common in young Australian adults. While short- and long-term risky drinking is more common in those with an alcohol use disorder, the majority of moderate- and high-risk drinking is done by those who do not meet criteria for an alcohol use disorder.

Teen smokers reach their mid twenties.

PURPOSE: Most outcome studies of adolescent smokers have focused on tobacco use in the short term. Few have reported on the health of adolescent smokers as they reach young adulthood. METHODS: The design was a 10-year, eight-wave cohort study of a state-wide community sample of 1943 participants in Victoria, Australia. Participants were initially aged 14 to 15 years. Tobacco use was assessed with self-reported frequency of use and a seven-day retrospective diary. The Fagerstrom Test for Nicotine Dependence was used to define nicotine dependence in young adulthood. A computerized interview assessment was used during the teens and in young adulthood. RESULTS: Former daily smokers in adolescence accounted for most cases of nicotine dependence and high-dose (10+ cigarettes per day) smoking in young adulthood. Other substance abuse and psychiatric morbidity in young adulthood were also markedly elevated in this group. This was most clearly evident for cannabis dependence, where close to two-thirds of all cases were formerly daily tobacco smokers. Male smokers were more likely to continue as young adults. Persistent symptoms of depression and anxiety during the teens predicted progression to nicotine dependence, as did having a parent smoking daily. CONCLUSIONS: The poor health outcomes of daily adolescent smokers as they reach young adulthood provide a rationale for greater tobacco control initiatives directed at early users. Clinical interventions might usefully consider factors such as psychiatric morbidity and parental smoking.

Reverse gateways? Frequent cannabis use as a predictor of tobacco initiation and nicotine dependence.

AIMS: To examine the risk posed by cannabis use in young people for tobacco use disorders. Specifically we examined whether cannabis use in non-smokers predicted later initiation of tobacco use and whether cannabis use predicted later nicotine dependence in tobacco users. DESIGN: A 10-year eight-wave cohort study. SETTING: State of Victoria, Australia. PARTICIPANTS: A community sample of 1943 participants initially aged 14-15 years. MEASUREMENTS: Self-report of tobacco and cannabis use was assessed in the teens using a computerized interview assessment and in young adulthood with a CATI assessment. The Fagerström Test for Nicotine Dependence was used to define nicotine dependence. FINDINGS: For teen non-smokers, at least one report of weekly cannabis use in the teens predicted a more than eightfold increase in the odds of later initiation of tobacco use (OR 8.3; 95% CI 1.9-36). For 21-year-old smokers, not yet nicotine-dependent, daily cannabis use raised the odds of nicotine dependence at the age of 24 years more than threefold (OR 3.6, 1.2, 10) after controlling for possible confounders, including level of tobacco use and subsyndromal signs of nicotine dependence. CONCLUSIONS: Weekly or more cannabis use during the teens and young adulthood is associated with an increased risk of late initiation of tobacco use and progression to nicotine dependence. If this effect is causal, it may be that a heightened risk of nicotine dependence is the most important health consequence of early frequent cannabis use.

Teenage drinking and the onset of alcohol dependence: a cohort study over seven years.

AIM: To determine whether adolescent alcohol use and/or other adolescent health risk behaviour predisposes to alcohol dependence in young adulthood. DESIGN: Seven-wave cohort study over 6 years. PARTICIPANT: A community sample of almost two thousand individuals followed from ages 14-15 to 20-21 years. OUTCOME MEASURE: Diagnostic and Statistical Manual volume IV (DSM-IV) alcohol dependence in participants aged 20-21 years and drinking three or more times a week. FINDINGS: Approximately 90% of participants consumed alcohol by age 20 years, 4.7% fulfilling DSM-IV alcohol dependence criteria. Alcohol dependence in young adults was preceded by higher persisting teenage rates of frequent drinking [odds ratio (OR) 8.1, 95% confidence interval (CI) 4.2, 16], binge drinking (OR 6.7, 95% CI 3.6, 12), alcohol-related injuries (OR 4.5 95% CI 1.9, 11), intense drinking (OR 4.8, 95% CI 2.6, 8.7), high dose tobacco use (OR 5.5, 95% CI 2.3, 13) and antisocial behaviour (OR 5.9, 95% CI 3.3, 11). After adjustment for other teenage predictors frequent drinking (OR 3.1, 95% CI 1.2, 7.7) and antisocial behaviour (OR 2.4, 95% CI 1.2, 5.1) held persisting independent associations with later alcohol dependence. There were no prospective associations found with emotional disturbance in adolescence. CONCLUSION: Teenage drinking patterns and other health risk behaviours in adolescence predicted alcohol dependence in adulthood. Prevention and early intervention initiatives to reduce longer-term alcohol-related harm therefore need to address the factors, including alcohol supply, that influence teenage consumption and in particular high-risk drinking patterns.

Long-term impact of the Gatehouse Project on cannabis use of 16-year-olds in Australia.

This study examined the impact of a school-based preventive intervention on cannabis use in adolescence, using a cluster-randomized trial of a multilevel intervention aimed at improving social relationships within schools by promoting change in school environment. Four waves of data were collected at baseline (1997, Year 8: mean age 13 years) and six, 18, and 30 months later (1999, Year 10: mean age 16 years). Self-reported substance use, school engagement, and sociodemographic data were collected using computer-administered questionnaires. Some 2.678(74%) Year 8 students participated (wave 1) with minimal attrition (10% by wave 4). Adjusting for baseline use, weak evidence existed for an intervention effect on the prevalence of any use at Year 10 (OR 0.75, 95% CI 0.54, 1.05) and incident weekly use (OR 0.72, 95% CI 0.39, 1.33). These effects were reduced after adjusting for confounders. Moderate evidence suggested an interaction effect between intervention group and tobacco use (p = 0.04), suggesting the intervention was more effective for non-smokers at baseline (Adj. OR 0.50, 95% CI 0.26, 0.98). This study indicates that a multi-level school-based program may provide an innovative direction for sustainable school interventions with the potential to reduce substance use.

Association between dependent smoking and a polymorphism in the tyrosine hydroxylase gene in a prospective population-based study of adolescent health.

This study reports pilot data on an association between tobacco dependence and a five-allele tetranucleotide repeat polymorphism in the first intron of the tyrosine hydroxylase (TH) gene. One hundred and twenty-six Australian adolescents who had participated in the Health in Transition Study (1993-1997), and who showed patterns of either dependent or nondependent smoking across four waves of data collection, consented to participation in the pilot study. The smoking status of those recruited was confirmed using a telephone-administered drug use questionnaire during 2000. Tobacco dependence was defined as smoking more than 6 days per week and more than 10 cigarettes per day during wave 5 (year 2000) and at least one prior wave ( n = 58). A second, more stringent phenotype included smoking within an hour of waking ( n = 37). The control group comprised adolescents who had used tobacco but had remained low-level social smokers across each wave of data ( n = 56). DNA was collected using a mouthwash procedure. Using the more strictly defined tobacco dependence phenotype, and after adjusting for sex, a significant protective association was found between the K4 allele and tobacco dependence (OR 0.27, 95% confidence interval [CI] 0.09, 0.82). No association was found using the liberal criteria of tobacco dependence (OR 0.51, 95% confidence interval [CI] 0.23, 1.2). These preliminary results replicate a previous association between tobacco use and the K4 allele of the TH gene (Lerman et al., 1997). The potential significance of including time to first cigarette in definitions of tobacco dependence and the possible role that these TH variants might play in tobacco dependence are discussed.

Adolescent precursors of cannabis dependence: findings from the Victorian Adolescent Health Cohort Study.

BACKGROUND: Dependence increases the likelihood of adverse consequences of cannabis use, but its aetiology is poorly understood. AIMS: To examine adolescent precursors of young-adult cannabis dependence. METHOD: Putative risk factors were measured in a representative sample (n=2032) of secondary students in the State of Victoria, Australia, six times between 1992 and 1995. Cannabis dependence was assessed in 1998, at age 20-21 years. RESULTS: Of 1601 young adults, 115 met criteria for cannabis dependence. Male gender (OR=2.6, P < 0.01), regular cannabis use (weekly: OR=4.9; daily: OR=4.6, P=0.02), persistent antisocial behaviour (linear effect P=0.03) and persistent cigarette smoking (linear effect P=0.02) independently predicted cannabis dependence. Neither smoking severity (P=0.83) nor persistent psychiatric morbidity (linear effect P=0.26) independently predicted dependence. Regular cannabis use increased risk only in the absence of persistent problematic alcohol use. CONCLUSIONS: Weekly cannabis use marks a threshold for increased risk of later dependence, with selection of cannabis in preference to alcohol possibly indicating an early addiction process.