Psychiatric and familial predictors of transition times between smoking stages: results from an offspring-of-twins study

Developmental considerations in survival models as applied to substance use research

Survival analysis is a class of models that are ideal for evaluating questions of timing of events, which makes them well-suited for modeling the development of a process such as initiation of substance use, development of addiction, or post-treatment recovery. The focus of this review paper is to demonstrate how survival models operate in a broader developmental framework and to offer guidance on selecting the appropriate model on the basis of the research question at hand. We provide a basic overview of survival models and then identify several key issues, explain how they pertain to research in the addiction field, and describe studies that utilize survival models to address questions about timing. We discuss the importance of carefully selecting the metric and origin of the time scale that corresponds to developmental process under investigation and we describe types of censoring/truncation. We describe the value of modeling covariates as time-invariant versus time-varying, and make the distinction between time-varying covariates and time-varying effects of covariates. We also explain how to test for substantive differences due to the timing of the assessment of the predictor. We finish the paper with a presentation of relatively novel extensions of survival models, including models that integrate standard statistical mediational analysis with discrete-time survival analysis, models that simultaneously consider order and timing of multiple events, and models that involve joint modeling of longitudinal and survival data. We also present our own substantive examples of various models in an Appendix containing annotated syntax and output.

Associations of parental alcohol use disorders and parental separation with offspring initiation of alcohol, cigarette and cannabis use and sexual debut in high-risk families

BACKGROUND AND AIMS

Parental alcohol use disorders (AUDs) and parental separation are associated with increased risk for early use of alcohol in offspring, but whether they increase risks for early use of other substances and for early sexual debut is under-studied. We focused on associations of parental AUDs and parental separation with substance initiation and sexual debut to (1) test the strength of the associations of parental AUDs and parental separation with time to initiation (age in years) of alcohol, tobacco and cannabis use and sexual debut and (2) compare the strength of association of parental AUD and parental separation with initiation.

DESIGN

Prospective adolescent and young adult cohort of a high-risk family study, the Collaborative Study on the Genetics of Alcoholism (COGA).

SETTING

Six sites in the United States.

PARTICIPANTS

A total of 3257 offspring (aged 14-33 years) first assessed in 2004 and sought for interview approximately every 2 years thereafter; 1945 (59.7%) offspring had a parent with an AUD.

MEASUREMENTS

Diagnostic interview data on offspring substance use and sexual debut were based on first report of these experiences. Parental life-time AUD was based on their own self-report when parents were interviewed (1991-2005) for most parents, or on offspring and other family member reports for parents who were not interviewed. Parental separation was based on offspring reports of not living with both biological parents most of the time between ages 12 and 17 years.

FINDINGS

Parental AUDs were associated with increased hazards for all outcomes, with cumulative hazards ranging from 1.19 to 2.71. Parental separation was also an independent and consistent predictor of early substance use and sexual debut, with hazards ranging from 1.19 to 2.34. The strength of association of parental separation with substance initiation was equal to that of having two AUD-affected parents, and its association with sexual debut was stronger than the association of parental AUD in one or both parents.

CONCLUSIONS

Parental alcohol use disorders (AUDs) and parental separation are independent and consistent predictors of increased risk for early alcohol, tobacco and cannabis use and sexual debut in offspring from families with a high risk of parental AUDs.

Military service and smoking in a cohort of northern Vietnamese older adults

OBJECTIVES

Wide-ranging scholarship demonstrates war's impacts on US veterans' health. We ask whether, among Vietnamese men of a certain age, wartime experiences contributed to initiating smoking, and thus shaped one behavioral pathway linking war exposure and older adult health.

METHODS

We analyze the Vietnam Health and Aging Pilot Study (VHAPS), a survey of adults ages 55 and older (N = 405) conducted in one commune of northern Vietnam. We implement Cox discrete-time proportional hazards models to discern the effects of military service upon the initiation of smoking.

RESULTS

Military service results in a heightened risk of initiating smoking within this cohort (HR 2.13, [CI 1.36, 3.35]). Smoking initiation is also significantly gendered and age graded. Socioeconomic position and social capital variables in the models are statistically insignificant.

CONCLUSIONS

This study finds that, among older northern Vietnamese men whose early adulthood coincided with mass mobilization in the Vietnam War, involvement in formal military service significantly increased the risk of initiating smoking. Military-induced smoking emerges where tobacco products were not provided by the military institution, but where social availability of tobacco was widespread.

Onset of opportunity to use cannabis and progression from opportunity to dependence: Are influences consistent across transitions?

BACKGROUND

There is a developing body of research looking at cannabis use opportunity, but little research examining timing of opportunity to use cannabis.

AIMS

Identify factors associated with (1) earlier opportunity to use cannabis and (2) faster progression from opportunity to cannabis dependence.

METHOD

Cross-sectional study of 3824 Australian twins and siblings, measuring age of onset of cannabis use opportunity and DSM-IV cannabis dependence. Survival analysis identified factors associated with faster progression to opportunity or dependence.

RESULTS

Factors associated with both speed of progression to opportunity and dependence were conduct disorder (opportunity HR 5.57, 95%CI 1.52-20.47; dependence HR 2.49, 95%CI 1.91-3.25), parental drug problems (opportunity HR 7.29, 95%CI 1.74-30.62; dependence HR 3.30, 95%CI 1.63-6.69), weekly tobacco use (opportunity HR 8.57, 95%CI 3.93-18.68; dependence HR 2.76, 95% CI 2.10-3.64), and female gender (opportunity HR 0.69, 95%CI 0.64-0.75; dependence HR 0.44, 95%CI 0.34-0.55). Frequent childhood religious attendance (HR 0.74, 95%CI 0.68-0.80), parental conflict (HR 1.09, 95%CI 1.00-1.18), parental alcohol problems (HR 1.19, 95%CI 1.08-1.30) and childhood sexual abuse (HR 1.17, 95%CI 1.01-1.34) were uniquely associated with transition to opportunity. Depressive episode (HR 1.44, 95%CI 1.12-1.85), tobacco dependence (HR 1.36, 95%CI 1.04-1.78), alcohol dependence (HR 2.64, 95%CI 1.53-4.58), other drug use (HR 2.10, 95%CI 1.64-2.69) and other drug dependence (HR 2.75, 95%CI 1.70-4.43) were uniquely associated with progression to dependence.

CONCLUSION

The profile of factors associated with opportunity to use cannabis and dependence only partially overlaps, suggesting targeting of interventions may benefit from being tailored to the stages of drug use.

Role of Temperament, Personality Traits and Onset Age of Smoking in Predicting Opiate Dependence

BACKGROUND

According to drug gateway theory, smoking cigarettes, especially, low onset age of smoking, is one of the risk factors for future use.

OBJECTIVES

The present study aimed to compare nicotine and opiate addicts to identify the differences in personality traits and onset age of smoking in the two groups that cause some individuals to appeal to other substances after starting to use cigarettes.

PATIENTS AND METHODS

Two groups of opiate and nicotine addicts were randomly selected. Revised version of the Cloninger temperament inventory questionnaire, the Fagrastrom nicotine dependence and the Maudsley addiction profile were used. ANOVA and logistic regression were applied for data analysis.

RESULTS

Opiate addicts had higher scores in novelty seeking dimension and lower scores in cooperativeness compared to nicotine addicts. The onset age of smoking cigarette in opiate addicts was lower than nicotine addicts.

CONCLUSIONS

Low onset age of smoking cigarettes, high novelty seeking and low cooperativeness in opiate dependents are among the important personality traits in future use of drugs that can predict the subsequent onset of using opiate drugs.

The association between speed of transition from initiation to subsequent use of cannabis and later problematic cannabis use, abuse and dependence

AIMS

To test whether speed of transition from initiation use to subsequent use of cannabis is associated with likelihood of later cannabis dependence and other outcomes, and whether transition speed is attributable to genetic or environmental factors.

DESIGN

Cross-sectional interview study.

SETTING

Australia.

PARTICIPANTS

A total of 2239 twins and siblings who reported using cannabis at least twice [mean age at time of survey = 32.0, 95% confidence interval (CI) = 31.9 - 32.1, range = 22-45].

MEASUREMENTS

Time between initiation and subsequent cannabis use (within 1 week; within 3 months; between 3 and 12 months; more than 1 year later), later use of cannabis and symptoms of DSM-IV cannabis abuse/dependence. Multinomial regression analyses (comparison group: more than 1 year later) adjusted the association between speed of transition and the outcomes of cannabis daily use, abuse/dependence and treatment-seeking after controlling for socio-demographic, childhood, mental health, peer and licit drug factors. Twin modelling estimated the proportion of variance in transition speed attributable to genetic (A), common environment (C) and unique environmental (E) factors.

FINDINGS

Subsequent use of cannabis within 1 week of initiation was associated with daily use [odds ratio (OR) = 2.64, 95% CI = 1.75-3.99], abuse and/or dependence (OR = 3.25, 95% CI = 2.31-4.56) and treatment-seeking for cannabis problems (OR = 1.89, 95% CI = 1.03-3.46). Subsequent use within 3 months was associated with abuse and/or dependence (OR = 1.61, 95% CI = 1.18-2.19). The majority of the variation of the speed of transition was accounted for by unique environment factors (0.75).

CONCLUSIONS

Rapid transition from initiation to subsequent use of cannabis is associated with increased likelihood of subsequent daily cannabis use and abuse/dependence.

Rate of progression from first use to dependence on cocaine or opioids: a cross-substance examination of associated demographic, psychiatric, and childhood risk factors

BACKGROUND

A number of demographic factors, psychiatric disorders, and childhood risk factors have been associated with cocaine dependence (CD) and opioid dependence (OD), but little is known about their relevance to the rate at which dependence develops. Identification of the subpopulations at elevated risk for rapid development of dependence and the risk factors that accelerate the course of dependence is an important public health goal.

METHODS

Data were derived from cocaine dependent (n=6333) and opioid dependent (n=3513) participants in a multi-site study of substance dependence. Mean age was approximately 40 and 40% of participants were women; 51.9% of cocaine dependent participants and 29.5% of opioid dependent participants self-identified as Black/African-American. The time from first use to dependence was calculated for each substance and a range of demographic, psychiatric, and childhood risk factors were entered into ordinal logistic regression models to predict the (categorical) transition time to CD and OD.

RESULTS

In both the cocaine and opioid models, conduct disorder and childhood physical abuse predicted rapid development of dependence and alcohol and nicotine dependence diagnoses were associated with slower progression to CD or OD. Blacks/African Americans were at greater risk than European Americans to progress rapidly to OD.

CONCLUSIONS

Only a subset of factors known to be associated with CD and OD predicted the rate at which dependence developed. Nearly all were common to cocaine and opioids, suggesting that sources of influence on the timing of transitions to dependence are shared across the two substances.

Dual growth of adolescent smoking and drinking: evidence for an interaction between the mu-opioid receptor (OPRM1) A118G polymorphism and sex

Smoking and alcohol use often co-occur during adolescence, but little is known about the codevelopment of these substances. In the search for etiological factors that help to explain the development of adolescent substance use patterns, studies have revealed substantial heritability for both alcohol use and smoking. In this regard, the µ-opioid receptor gene (OPRM1, chromosome 6q24-q25) has been linked to both substances. This study examined the predictive relationships between initial level and growth of smoking and drinking in 311 early adolescents (13-15 years old) over a 4-year period. In addition, the effects of the A118G polymorphism of the OPRM1 gene on the initial values and the development over time of alcohol use and smoking were assessed. Finally, as prevalence and heritability estimates for both alcohol- and smoking-related behaviors differ between males and females, OPRM1 by sex interactions were tested. We found that high initial levels of early adolescent alcohol consumption were related to a stronger increase in smoking levels over time. In contrast, high initial levels of smoking were not related to growth of alcohol use. No main OPRM1 effects were found, but sex-specificity of the gene was found for smoking development. Male A-allele carriers showed a faster development in smoking behavior, whereas in females, the G-allele led to a faster development in smoking. Thus, in addition to high levels of alcohol as a risk factor for the development of smoking behavior, sex-specific effects exist for OPRM1, which may additionally have consequences for the development of adolescent smoking.

Alcohol consumption in men is influenced by qualitatively different genetic factors in adolescence and adulthood

BACKGROUND

Alcohol consumption is influenced by genetic factors. Previous studies have examined the heritability of alcohol consumption, or related phenotypes, from adolescence into adulthood, frequently finding that total heritability changes over time. However, it remains unclear whether the same genes underlie liability to alcohol consumption across development versus whether novel risk genes become important over time. Method A population-based study of adult male twins (n=1790) born in Virginia, USA, retrospectively reported on their average monthly alcohol consumption from early adolescence through adulthood. We used twin modeling methods to explore genetic and environmental influences on alcohol consumption over time.

RESULTS

One latent genetic factor accounted for the majority of the heritability in alcohol consumption during mid- to late adolescence, but its influence declined thereafter; from young adulthood forward, heritability was largely attributable to a second genetic factor. The total heritability of alcohol consumption increased from 0 at ages 12-14 years to 0.40 by ages 18-21 years. Shared environmental factors declined in influence over time.

CONCLUSIONS

The heritability of alcohol consumption over time is dynamic both quantitatively and qualitatively. These results have important implications for gene identification endeavors. Furthermore, these findings could inform efforts to elucidate developmentally dynamic behaviors, such as antisocial behavior.

Childhood sexual abuse and early substance use in adolescent girls: the role of familial influences

AIM

To assess the extent to which the association between childhood sexual abuse (CSA) and early use of alcohol, cigarettes and cannabis in adolescent girls is mediated by risk factors that tend to cluster in families where CSA occurs.

DESIGN

An abridged version of the Semi-Structured Assessment for the Genetics of Alcoholism (SSAGA) was administered by telephone.

PARTICIPANTS

A total of 3761 female twins aged 18-29 (14.6% African American, 85.4% European American).

MEASUREMENTS

CSA experiences and history of substance use were queried in the SSAGA-based interviews.

FINDINGS

After controlling for familial influences on early substance use by including co-twin early use status in models, separate Cox proportional hazards regression analyses predicting onset of alcohol, cigarette and cannabis use revealed a significant association with CSA. The effect was observed to age 19 years for cigarettes and to age 21 years for cannabis, but was limited to age 14 years or younger for alcohol, with the most pronounced risk before age 10 [hazard ratio (HR) = 4.59; confidence interval (CI): 1.96-10.74]. CSA-associated risk for initiation of cigarette and cannabis use was also highest in the youngest age range, but the decline with age was much more gradual and the hazard ratios significantly lower (HR: 1.70; CI: 1.13-2.56 for cigarettes and HR: 2.34, CI: 1.57-3.48 for cannabis).

CONCLUSIONS

Childhood sexual abuse history is a distinct risk factor for use of cigarettes and cannabis, and a very strong predictor of early age at first drink.

Differences in time to onset of smoking and nicotine dependence by race/ethnicity in a Midwestern sample of adolescents and young adults from a high risk family study

OBJECTIVE

The objective of this study was to determine whether race/ethnicity was associated with time to smoking initiation and time from first cigarette to onset of DSM-IV nicotine dependence (ND) after adjusting for familial and individual psychosocial risk factors.

METHODS

Cox proportional hazards models with time-dependent covariates were used to analyze data from 1376 offspring aged 12-33 years from 532 families at high risk for substance use problems due to paternal alcohol problems and 235 low risk families. Fifty-six percent of the sample self-identified as African-American (AA) and 44% were mainly of European descent.

RESULTS

Controlling for covariates, AAs began smoking at older ages (HR=0.58; 95% CI: 0.48-0.70) and had longer times between smoking initiation and onset of ND compared to non-AAs (HR=0.25, 95% CI: 0.16-0.39 for ND onset occurring <18 years and HR=0.49, 95% CI: 0.30-0.80 for ND onsets ≥ age 18). After additionally controlling for number of cigarettes smoked daily, the racial/ethnic effects for onset of ND were attenuated, but remained statistically significant for ND onset <18 (HR=0.34, 95% CI: 0.19-0.61); however, the estimate was no longer significant for later ND onset (HR=0.84, 95% CI: 0.50-1.41).

CONCLUSIONS

AA adolescents and young adults initiate smoking at older ages and have longer transition periods between initiation and onset of ND compared to non-AAs, even after controlling for many relevant psychiatric and psychosocial covariates; however, racial/ethnic differences in time to onset of nicotine dependence in late adolescence and young adulthood may be explained by differences in daily quantity smoked.

Alcohol use in adolescence and risk of disability pension: a 39 year follow-up of a population-based conscription survey

BACKGROUND

The role of alcohol consumption for disability pension (DP) is controversial and systematic reviews have not established causality. We aimed to assess the role of adolescent alcohol use for future DP. We wanted to find out whether an increased risk mainly would affect DP occurring early or late in life as well as whether the level of alcohol consumption and patterns of drinking contribute differently in DP receiving.

METHODOLOGY/PRINCIPAL FINDINGS

The study is a 39-year follow-up of 49 321 Swedish men born in 1949-1951 and conscripted for compulsory military service in 1969-1970. As study exposures (i) "risk use" of alcohol composed of measures related to pattern of drinking, and (ii) the level of consumption based on self-reported volume and frequency of drinking had been used. Information on DP was obtained from social insurance databases through 2008. "Risk use" of alcohol was associated with both "early DP" and "late DP", i.e. granted below and above the approximate age of 40 years, with crude hazard ratio (HR) of 2.89 (95% confidence intervals (CI) 2.47-3.38) and HR of 1.87 (95%CI: 1.74-2.02), respectively. After adjustment for covariates, HR was reduced to 1.32 (95%CI: 1.09-1.59) and 1.14 (95%CI: 1.05-1.25), respectively. Similar patterns were seen for moderate (101-250 g 100% alcohol/week) and high (>250 g) consumption, though the risk disappeared when fully adjusted.

CONCLUSIONS/SIGNIFICANCE

Alcohol use in adolescence, particularly measured as "risk use", is associated with increased risk of future DP. The association is stronger for "early DP", but remains significant even for DP granted in older ages. Therefore, pattern of drinking in adolescent should be considered an important marker for future reduced work capacity.

Cannabis use stages as predictors of subsequent initiation with other illicit drugs among French adolescents: use of a multi-state model

The aim of this study was to confirm the influence of cannabis use patterns on the probability of initiation with other illicit drugs (OID). A French nationwide retrospective cohort on drug use was reconstituted on 29,393 teenagers. A Markov multi-state model was fitted, modelling all possible pathways from initial abstinence to cannabis initiation, daily cannabis use and OID initiation. The model was adjusted for tobacco and alcohol use. The risk for OID initiation appeared 21 times higher among cannabis experimenters and 124 times higher among daily cannabis users than among non-users. Tobacco and alcohol use were associated with a greater risk of moving on to cannabis initiation (hazard ratio (HR)=1.2 for tobacco initiation, HR=2.6 for daily tobacco use and HR=2.8 for drunkenness initiation). The results of this study provide a confirmation of a stage process in drug use, mediated by cannabis and liable to lead to OID experiment. This is compatible with the literature on the gateway theory, but goes further by modelling the entire sequence of use. OID experiment could be a consequence of initial opportunity to use the more accessible illicit drug, cannabis.

Body mass index and regular smoking in young adult women

Little is known about the relationship between relative body weight and transition from experimentation to regular smoking in young adult women. In the current study, data from 2494 participants in wave 4 of the Missouri Adolescent Female Twin Study (aged 18-29years) who reported ever smoking a cigarette were analyzed using logistic regression. Body mass index (BMI) at time of interview was categorized according to CDC adult guidelines, and regular smoking was defined as having ever smoked 100 or more cigarettes and having smoked at least once a week for two months in a row. Since the OR's for the overweight and obese groups did not differ significantly from one another in any model tested, these groups were combined. Forty-five percent of women who had ever smoked had become regular smokers. Testing of interactions between potential covariates and levels of the categorical BMI variable revealed a significant interaction between overweight/obesity and childhood sexual abuse (CSA; p<0.001) associated with regular smoking. Among women reporting CSA, the association between overweight/obesity and having become a regular smoker was negative (n=374; OR=0.48, 95% CI: 0.28-0.81). Both underweight and overweight/obesity were positively associated with transition to regular smoking among women who did not report CSA (n=2076; OR=1.57, 95% CI: 1.05-2.35 and OR=1.73, 95% CI: 1.35-2.20, respectively). These results suggest that experiencing CSA alters the association between BMI and regular smoking in women who have experimented with cigarettes.

Disruptive symptoms in childhood and adolescence and early initiation of tobacco and cannabis use: the Gazel Youth study

PURPOSE

To examine the link between symptoms of hyperactivity-inattention and conduct disorder in childhood, and the initiation of tobacco and cannabis use, controlling for other behavioral symptoms, temperament and environmental risk factors.

METHOD

The sample (N=1107 participants, aged 4 to 18 years at baseline) was recruited from the population-based longitudinal Gazel Youth study with a follow-up assessment 8 years later. Psychopathology, temperament, environmental variables, and initiation of tobacco and cannabis use were self-reported. Event time analyses were performed to assess the effects of childhood disruptive symptoms on age at first use of tobacco and cannabis.

RESULTS

Proportional hazard models revealed that participants with high levels of childhood symptoms of both hyperactivity-inattention and conduct disorder were at highest risk of early tobacco initiation (in males: hazard ratio [HR]=2.05; confidence interval [CI]: 1.24-3.38; in females: HR=2.01; CI: 1.31-3.09), and, in males, of early cannabis initiation (HR=1.95; CI: 1.04-3.64). Temperament, through activity in both males and females and negative emotionality in females, was also associated to early substance use initiation.

CONCLUSIONS

Children who simultaneously have high levels of symptoms of hyperactivity-inattention and conduct disorder are at increased risk for early substance initiation. These associations may guide childhood health professionals to consider the liability for early substance initiation in high-risk groups.

Initial response to cigarettes predicts rate of progression to regular smoking: findings from an offspring-of-twins design

The aim of this study was to examine the association between initial subjective effects from cigarettes and the rate of progression from first cigarette to regular smoking. Latent class analysis (LCA) was applied to subjective effects data from 573 offspring of twins ranging in age from 14 to 32 years. LCA revealed four classes: 1) High on both pleasurable and physiological responses, 2) Cough only response, 3) High on physiological, low on pleasurable responses, and 4) High on pleasurable, low on physiological responses. Classes of responses were then used to predict time from first cigarette to the onset of regular smoking in a Cox proportional hazards model. Time-varying covariates representing relevant psychiatric and psychosocial factors as well as dummy variables representing the offspring-of-twins design were included in the model. Members of classes 1 and 4 transitioned more rapidly to regular smoking than the classes characterized as low on the pleasurable response dimension. Our findings provide evidence that previously reported associations between pleasurable initial experiences and progression to regular smoking hold true as well for the rate at which that transition occurs. Furthermore, the fact that profiles of responses did not fall into global categories of exclusively pleasurable vs. exclusively negative (physiological) responses suggests the importance of considering both dimensions in combination to characterize risk for smoking-related outcomes.

Testing the equal environments assumption in the Children of Twins design

In a Children of Twins (COT) design, the environmental and genetic risk of a child is, in part, dependent upon the status of the father and the father's cotwin. The logic of the COT method breaks down if the zygosity of the twin pair is confounded with the environment provided to the child (a version of the Equal Environment Assumption, EEA). If MZ twin fathers see each other more often than DZ twin fathers, and a child's uncle is the affected twin in discordant pairs, this could increase the environmental risk of children of MZ over that of DZ discordant twins. The current study was designed to test the EEA in the COT design, specifically in children of alcohol and drug dependent fathers. Results indicated that MZ twins did have more contact than DZ twins. Regression analyses were conducted to predict child externalizing symptom counts from father's zygosity group status, level of contact with father's cotwin, and their interaction. Results found no significant interaction between father's zygosity and the higher level of cotwin contact (seen in MZ twins) in predicting several measures of offspring externalizing risk. The results of this study suggested that the COT design does not confound zygosity with differences in environmental risk exposure, findings that support the validity of the EEA within this research context.

Emotional, behavioural problems and cigarette smoking in adolescence: findings of a Greek cross-sectional study

Background

Although several studies have reported findings concerning the association between smoking and emotional/behavioural problems, little research has investigated this association after controlling for confounding factors which have been found to be significantly correlated with both cigarette smoking and emotional/behavioural problems and may have a strong effect on the relationship between adolescents' mental health and smoking. The present study attempted to assess the association between adolescents' smoking status and their emotional/behavioural problems after controlling for a number of possible confounders (i.e. age, gender, parental smoking status, exposure to family smoking, family socioeconomic status, adolescents' leisure time) in a Greek nation-wide school-based sample.

Methods

Participants completed a questionnaire which retrieved information about age, gender, family socioeconomic status, smoking status, parental smoking, adolescents' leisure time and emotional/behavioural problems. Data were modelled using multiple logistic regression analysis with adolescents' smoking status as the dependent variable.

Results

A total of 1194 (i.e. 63% response rate) of self-reported questionnaires (40.1% boys, 59.9% girls; 12-18 years old) were returned. Data from 1030 participants with full data were analyzed. Cigarette smoking was strongly associated with higher levels of emotional/behavioural problems (p < 0.001) and the association was not moderated (OR = 1.13, 95% CI: 1.08-1.18) after controlling for the effects of other covariates. Emotional symptoms, conduct problems and hyperactivity/inattention were all significantly associated with adolescents' current smoking.

Conclusions

This study supports the association between smoking and emotional/behavioural problems among adolescents. Addressing adolescents' needs regarding their emotional/behavioural health could be helpful in the development of effective anti-smoking strategies in school environment and elsewhere.

Externalizing behavior problems and cigarette smoking as predictors of cannabis use: the TRAILS Study

OBJECTIVE

To examine externalizing behavior problems and cigarette smoking as predictors of subsequent cannabis use.

METHOD

Dutch adolescents (N = 1,606; 854 girls and 752 boys) from the TRacking Adolescents' Individual Lives Survey (TRAILS) ongoing longitudinal study were examined at baseline (ages 10-12 [T1]) and at two follow-up assessments (ages 12-15 [T2] and 15-18 [T3]). The analysis focused on DSM-IV externalizing behavior (conduct, attention deficit hyperactivity, and oppositional) problems at T1, assessed by the Youth Self Report and the Child Behavior Check List, on self-reported ever smoking at T2, and on cannabis use at T3.

RESULTS

All associations of parent-rated externalizing behavior problems with cannabis were mediated by earlier smoking. Considering self-reported problems, none of these associations with cannabis were mediated by smoking, except the influence of self-reported conduct problems in girls. Interestingly, even after adjusting for externalizing problems, earlier smoking independently and consistently predicted cannabis use. The adjusted odds ratios for smoking varied in boys from 4.8 to 5.2 (ever) from 10 to 12 (daily) and from 22 to 23 (early-onset) whereas in girls from 4.9 to 5.0, 5.6 to 6.1, and 27 to 28, respectively (p <.001 for all).

CONCLUSIONS

Our findings challenge the view that externalizing behavior problems directly predict cannabis initiation. Such associations were inconsistent across informants and sexes and were often mediated by earlier smoking. Early smoking onset is a powerful predictor of later cannabis initiation independent of preceding externalizing behavior problems. Although externalizing behavior problems are important as a starting point for substance use trajectories, early-onset smoking should be identified as an important marker of cannabis use risk.

Common genetic influences on the timing of first use for alcohol, cigarettes, and cannabis in young African-American women

The risks associated with early age at initiation for alcohol, cigarette, and cannabis use are well documented, yet the timing of first use has rarely been studied in genetically informative frameworks, leaving the relative contributions of genetic and environmental factors to age at initiation largely unknown. The current study assessed overlap in heritable and environmental influences on the timing of initiation across these three substances in African-American women, using a sample of 462 female twins (100 monozygotic and 131 dizygotic pairs) from the Missouri Adolescent Female Twin Study. Mean age at the time of interview was 25.1 years. Ages at first use of alcohol, cigarettes, and cannabis were gathered in diagnostic interviews administered over the telephone. Standard genetic analyses were conducted with substance use initiation variables categorized as never, late, and early onset. Variance in the timing of first use was attributable in large part to genetic sources: 44% for alcohol, 62% for cigarettes, and 77% for cannabis. Genetic correlations across substances ranged from 0.25 to 0.70. Shared environmental influences were modest for alcohol (10%) and absent for cigarettes and cannabis. Findings contrast with reports from earlier studies based on primarily Caucasian samples, which have suggested a substantial role for shared environment on substance use initiation when measured as lifetime use. By characterizing onset as timing of first use, we may be tapping a separate construct. Differences in findings may also reflect a distinct etiological pathway for substance use initiation in African-American women that could not be detected in previous studies.

Psychiatric aspects of chronic lung disease

Chronic lung diseases continue to be common and cause significant morbidity and mortality. There is a complex interplay between psychiatric issues and pulmonary diseases. This review aims to summarize the recent literature and advances involving psychiatric aspects of lung diseases, including chronic obstructive pulmonary disease, asthma, restrictive lung disease, and cystic fibrosis. The authors include the latest findings in epidemiology, impact, etiology, screening, and management of psychiatric and pulmonary comorbidity. The relationship between mental health and lung disease, as it is between mental health and other physical illnesses, is multifactorial. Further studies continue to clarify issues and treatment guidelines for this comorbidity.

Transitions to regular smoking and to nicotine dependence in women using cannabis

BACKGROUND

While there is substantial support in the literature for an increased prevalence of cannabis use in cigarette smokers, emerging studies allude to the possibility that cannabis users may, in turn, be at significantly elevated risk for rapid transitions in their cigarette smoking trajectories. If there is evidence in its favor, the increased rates of cigarette smoking in cannabis users may prove to be the most significant public health problem associated with cannabis use.

METHODS

In a sample of 3787 female twins (age range 18-29 years), we examined, using discrete-time survival analyses, whether women who reported cannabis use were at increased risk for regular cigarette smoking and progression to nicotine dependence.

RESULTS

After controlling for a large number of potential covariates, we found that women who used cannabis were at 4.4 and 2.8 increased hazards for transitioning from initiation to regular smoking and from regular smoking to nicotine dependence, respectively.

CONCLUSIONS

Cannabis use is associated with transitions to more involved stages of cigarette smoking in women. This is a source of public health concern, first due to the high mortality associated with cigarette smoking and second, due to the high prevalence of cannabis use in the general population.