A cotwin-control analysis of drug use and abuse/dependence risk associated with early-onset cannabis use

We assessed whether, after controlling for genetic and shared environmental influences, early cannabis use remains a significant predictor of other drug use, abuse, and dependence, and whether the risk for early-users is greater than that for later cannabis users. Data from a 1992 telephone diagnostic interview of 8169 male twins (M = 42.0 years at interview) who served in the U.S. military during the Vietnam-era were used to identify a subsample of 293 monozygotic (MZ) and dizygotic (DZ) twin pairs discordant for early cannabis use (before age 18). Using cotwin-control analyses, outcomes assessed were: lifetime illegal drug use (stimulant/cocaine, sedative, opiate, and hallucinogen/PCP), lifetime DSM-III-R illegal drug abuse/dependence, and lifetime DSM-III-R alcohol dependence. After controlling for covariates, early cannabis users were at greater risk than their later/never-using cotwins for 8 of 9 substance-related comparisons, including: using other illegal drugs (ORs: 2.71–4.09), having illegal drug abuse/dependence (ORs: 2.02–2.13), and developing alcohol dependence (OR = 2.36). When analyses were limited to pairs in which the cotwin used cannabis later, early and later-users only differed significantly on sedative, opiate, and hallucinogen use. After familial influences on early cannabis use were controlled for, cannabis use—regardless of the age of initiation—still conferred increased risk of other illegal drug use, drug abuse/dependence, and alcohol dependence. In contrast to previous research, there is limited evidence for increased risk associated with early-onset use in this sample of Vietnam-era veterans.     

Duration of cannabis use - a novel phenotype?

Although cannabis is the most commonly used illicit drug, duration of cannabis use is typically short, with many of those who initiate cannabis use ceasing use by their late twenties. In this paper we analyze data from a volunteer Australian cohort of 6265 male and female twins to examine whether the duration of cannabis use is an informative phenotype for future genetic analyses. Genetic modeling indicated: (a) moderate genetic influences on duration of cannabis use in both males (41%; 95% CI=31-51) and females (55%; 95% CI=46-63); (b) strong genetic influences on cannabis dependence in both males (72%, 95% CI=61-81) and females (62%, 95% CI=48-74); (c) no evidence of shared environmental influences on duration of cannabis use or on cannabis dependence in either males or females. Importantly, this model fitting indicated that a substantial component of genetic influences (rg=.90, 95% CI=.77-.99 (males); .70, 95% CI=.57-.83 (females)) on duration of cannabis use was shared with those influencing liability to cannabis dependence. While there were high genetic correlations in both women and men, lifetime duration of cannabis may be uniquely informative in assessing components of liability to cannabis use.     

Illicit drug use and abuse/dependence: modeling of two-stage variables using the CCC approach

Drug use and abuse/dependence are stages of a complex drug habit. Most genetically informative models that are fit to twin data examine drug use and abuse/dependence independent of each other. This poses an interesting question: for a multistage process, how can we partition the factors influencing each stage specifically from the factors that are common to both stages? We used a causal-common-contingent (CCC) model to partition the common and specific influences on drug use and abuse/dependence. Data on use and abuse/dependence of cannabis, cocaine, sedatives, stimulants and any illicit drug was obtained from male and female twin pairs. CCC models were tested individually for each sex and in a sex-equal model. Our results suggest that there is evidence for additive genetic, shared environmental and unique environmental influences that are common to illicit drug use and abuse/dependence. Furthermore, we found substantial evidence for factors that were specific to abuse/dependence. Finally, sexes could be equated for all illicit drugs. The findings of this study emphasize the need for models that can partition the sources of individual differences into common and stage-specific influences.     

Heritability of cannabis initiation in Dutch adult twins

Previous studies exploring the heritability of cannabis initiation have been carried out in the United States, Australia and United Kingdom. In the present study we assess cannabis initiation in The Netherlands, where the use of cannabis in small amounts is permitted. The sample included 3115 twins with a mean age of 27.4 years (SD 4.7) who are registered with the Netherlands Twin Register (NTR). Individual differences in cannabis initiation showed moderate genetic influences (44%). The remaining variance was explained by environmental influences shared by twins (31%) and by unique environmental factors (24%). Compared to studies from other countries, these results suggest that the relative importance of genetic and environmental factors is not different in a country with a more liberal cannabis policy.     

Alcohol and cannabis abuse/dependence symptoms and life satisfaction in young adulthood

Introduction and Aims. To examine the associations between substance abuse/dependence symptoms and life satisfaction, before and after adjustment for fixed and time‐dynamic sources of confounding. Design and Methods. Data were drawn from a 30 year longitudinal study of a birth cohort of 987 individuals. Associations between alcohol abuse/dependence symptoms, cannabis abuse/dependence symptoms and life satisfaction were examined using repeated measures regression models. Associations were adjusted for fixed and time‐dynamic sources of confounding, including family background, personality, demographics, recent life events, current employment and recent mental illness. Results. There were significant associations between alcohol abuse/dependence and life satisfaction (P < 0.0001) and between cannabis abuse/dependence and life satisfaction (P < 0.0001). These significant associations remained after adjustment for fixed sources of confounding. However, adjusting for time‐dynamic sources of confounding substantially reduced the associations. After adjustment for time‐dynamic sources of confounding there were no significant associations between alcohol abuse/dependence and life satisfaction (P > 0.17) or cannabis abuse/dependence and life satisfaction (P > 0.25). Discussion and Conclusions. These findings suggest that associations between life substance abuse/dependence and life satisfaction can be explained by time‐dynamic factors, such as employment, life events and comorbid mental illness that are associated with reduced life satisfaction. When due allowance is made for confounding, alcohol and cannabis abuse/dependence are not associated with reduced life satisfaction. [Swain NR, Gibb SJ, Horwood LJ, Fergusson DM. Alcohol and cannabis abuse/dependence symptoms and life satisfaction in young adulthood. Drug Alcohol Rev 2012;31:327–333]     

Tobacco, alcohol and drug use in eight- to sixteen-year-old twins: the Virginia Twin Study of Adolescent Behavioral Development.

OBJECTIVE: This study reports prevalences of lifetime and current alcohol, tobacco and drug use in adolescents; examines associations between substance use and a number of putative risk factors; and estimates the contribution of genetic, shared and unique environmental influences on substance use. METHOD: Substance use data were collected using the Child and Adolescent Psychiatric Assessment on a population sample of 1,412 male and female monozygotic and dizygotic twin pairs, aged 8 through 16, from the Virginia Twin Study of Adolescent Behavioral Development. RESULTS: Heritabilities were estimated to be 84% and 82% for liability to lifetime and current tobacco use, respectively. For alcohol use the role of genes and environment varied according to the context of reporting. Liability to lifetime alcohol use was estimated to be under environmental control, with 71% of the variation shared by members of a twin pair and 29% unique to individual twins. Lifetime alcohol use without the permission of a parent or guardian and current use of alcohol were predominantly explained by genetic factors (h2 = 72% and 74%). The role of genetic factors increased and that of unique environmental factors decreased with increasing severity of alcohol use. Lifetime use of any drug showed a heritability of 45%, with the shared environment accounting for 47% of the variation. Shared environmental factors explained most of the variation in marijuana use. CONCLUSIONS: Genetic factors explained a significant proportion of the variation in the use of tobacco, alcohol and other drugs. Shared environmental factors contributed significantly to lifetime alcohol use and other drug use.     

Early environmental influences contribute to covariation between internalizing symptoms and alcohol intoxication frequency across adolescence

The association between alcohol use and internalizing symptoms during adolescence varies across studies, and the causes underlying this association remain unclear. The current study examines the relationship between symptoms of anxiety and depression and intoxication frequency in a sample of Swedish twins assessed longitudinally from ages 13-14 to 19-20. The objectives of the study were to assess the stability of genetic and environmental influences on each trait across adolescence; to investigate whether these traits share genetic and/or environmental liabilities; and to explore quantitative changes in the shared liability over time. We found that the magnitude of genetic influences on internalizing symptoms remained relatively stable across adolescence, while their impact on intoxication frequency was dynamic. Symptoms of anxiety and depression were influenced by unique environmental factors, while both shared and unique environmental factors influenced intoxication frequency. Genetic and environmental innovation and attenuation were observed for both traits. While no significant genetic correlation was observed between traits, unique environmental factors did contribute to a shared liability. This environmental correlation was positive and moderate (r(E)=0.41) in the early assessment, but decreased and changed direction at later waves (r(E)=-.04 to -.01). The genetic and environmental factors underlying internalizing symptoms and intoxication frequency appear to be developmentally dynamic. Early environmental factors contribute to the association between these traits, but this shared liability diminishes across adolescence.     

Diagnostic orphans for alcohol use disorders in a treatment-seeking psychiatric sample

Individuals who endorse one or two of the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV) criterion items for alcohol dependence but do not meet criteria for either alcohol abuse or dependence have been referred to in the literature as "diagnostic orphans." The goal of the present study is to compare diagnostic orphans for alcohol use disorders (AUD) to patients with lifetime DSM-IV alcohol abuse, alcohol dependence, and those with no-AUD symptoms on a series of demographic, diagnostic, and clinical measures. Participants were treatment-seeking psychiatric outpatients (n=1793; 61.5% women) who completed an in-depth, face-to-face diagnostic evaluation for DSM-IV axis I and axis II disorders. Results revealed that diagnostic orphans were younger, had a higher frequency of family history positive for alcoholism, and higher rates of cannabis dependence, as compared to the no-AUD symptoms group. Diagnostic orphans differed significantly from patients with alcohol abuse and dependence on a number of demographic, diagnostic, and clinical measures. Most notably, on a lifetime basis, diagnostic orphans were less likely to meet diagnostic criteria for various substance use disorders, as compared to individuals with alcohol abuse and dependence. Taken together, these results generally do not support combining diagnostic orphans to individuals with alcohol abuse.     

The structure of cannabis dependence in the community

BACKGROUND: Cannabis is the most widely used illicit drug in developed countries, and has a significant impact on mental and physical health in the general population. However, the validity of common diagnostic schemes and their applicability to cannabis abuse and dependence is poorly understood. This paper describes a confirmatory factor analysis of the DSM-IV cannabis abuse and dependence criteria, using general population data. METHODS: Data from cannabis users (n=722) were obtained from a cross-sectional study of a large and representative sample of the Australian general population. The DSM-IV criteria for cannabis abuse and dependence were assessed using the CIDI-AUTO. RESULTS: Approximately, one in 12 Australians (7.1%) had used cannabis more than five times in the past 12 months and 56.5% of these reported at least one DSM-IV cannabis abuse or dependence criteria. Within the adult population, 2.2% met criteria for a cannabis use disorder (0.7% abuse and 1.5% dependence). Confirmatory factor analysis indicated that both a one- and two-factor model for cannabis use disorder provided an adequate fit to the data. However, the estimated correlation between the abuse and dependence factors in the two-factor model was extremely high (0.99). CONCLUSIONS: A one-factor model provided the most parsimonious model of the cannabis abuse and dependence criteria.     

Is the relationship between early-onset cannabis use and educational attainment causal or due to common liability?

Background

Several studies have shown that early cannabis use is correlated with poor educational performance including high school drop-out. The predominant explanation for this relationship is that cannabis use causes disengagement from education. Another explanation is that the association between early cannabis use and educational attainment is not causal, but the result of overlapping risk factors that increase the likelihood of both early cannabis use and disengagement from education. These confounding factors could be of genetic and/or environmental origin.

Methods

Here we use data from a large community-based sample of adult twins (N = 3337) who completed a comprehensive semi-structured telephone interview. We first apply the classical twin-design to determine whether genetic and/or environmental influences underlie the relationship between early-onset cannabis use (prior to age 18) and early school leaving. Next, with a co-twin control design we investigate whether the relationship between the two variables is more likely due to direct causality or overlapping risk factors.

Results

We find a significant phenotypic correlation between early-onset cannabis use and early school leaving (r = 0.26), which could be explained by familial influences (of genetic and/or shared environmental origin). The pattern of odds ratios found in the co-twin control design is not consistent with direct causation, but rather suggests that the association is due to shared environmental factors influencing both variables.

Conclusion

Our findings suggest that the relationship between early-onset cannabis use and school leaving is due to shared environmental risk factors influencing both the risk of early-onset cannabis use and early school leaving.     

DSM-IV criteria-based clinical subtypes of cannabis use disorders: results from the National Epidemiological Survey on Alcohol and Related Conditions (NESARC)

Prior research documented high homogeneity of alcohol use disorders (AUDs) as clinical entities. However, it is unknown whether this finding extends to other substance use disorders. We investigated this by examining the prevalence of all possible DSM-IV criteria-based clinical subtypes of current and lifetime cannabis use disorders in the general population. The number of possible (i.e., theoretical) clinical subtypes of cannabis abuse and dependence based on different combinations of the DSM-IV criteria was calculated using the combinatorial function. This number was compared with the subtypes actually observed in the National Epidemiologic Survey on Alcohol and Related Conditions (NESARC), a large U.S. national sample (N=43,093). Clinical and demographic correlates of the subtypes were examined with chi2 tests whose target population was the United States civilian non-institutionalized population. All DSM-IV cannabis abuse and dependence criteria were assessed with the Alcohol Use Disorder and Associated Disabilities Interview Schedule-DSM-IV Version (AUDADIS-IV). Of all possible cannabis dependence subtypes, 29 (69%) were observed in the 12-month timeframe, and 41 (98%) in the lifetime timeframe. The corresponding numbers of subtypes for cannabis abuse were 12 (75%), current and 15 (100%), lifetime. These findings suggest that, in contrast to alcohol disorders, cannabis use disorders were highly heterogeneous. Future research should investigate whether there are differences in the course and treatment response of these clinical subtypes of cannabis use disorders, and the heterogeneity of other substance use disorders.     

The natural course of cannabis use, abuse and dependence over four years: a longitudinal community study of adolescents and young adults.

OBJECTIVES: To determine incidence and patterns of natural course of cannabis use and disorders as well as cohort effects in a community sample of adolescents and young adults. METHOD: Cumulative incidence and patterns of cannabis use and disorders were examined in a prospective longitudinal design (mean follow-up period=42 months) in a representative sample (N=2446) aged 14-24 years at the outset of the study. Patterns of cannabis use, abuse and dependence (DSM-IV) were assessed with the Composite International Diagnostic Interview (M-CIDI). RESULTS: (1) Cumulative lifetime incidence for cannabis use (at second follow-up): 47%; 5.5% for cannabis abuse, 2.2% for dependence. (2) Men used and abused cannabis more often than women. (3) The majority of the older participants (18-24 years at baseline) had reduced their cannabis use at follow-up, while younger participants (14-17 years at baseline) more often had increased their use and developed abuse or dependence. (4) The younger birth cohort (1977-1981) tended to start earlier with substance (ab)use compared to the older birth cohort (1970-1977). (5) Cannabis use was associated with increasing rates of concomitant use of other licit and illicit drugs. CONCLUSIONS: Cannabis use is widespread in our sample, but the probability of developing cannabis abuse or dependence is relatively low (8%). The natural course of cannabis use is quite variable: about half of all cannabis users stopped their use spontaneously in their twenties, others report occasional or more frequent use of cannabis.     

The developmental antecedents of illicit drug use: evidence from a 25-year longitudinal study

BACKGROUND: The present study examined the developmental antecedents of illicit drug use and abuse/dependence. METHODS: A 25-year prospective longitudinal study of the health, development, and adjustment of a birth cohort of 1265 New Zealand children. Measures included assessments of adolescent and young adult illicit drug use and abuse/dependence; cannabis use to age 25; measures of parental adjustment; measures of exposure to childhood sexual abuse, physical abuse, and interparental violence; novelty-seeking; childhood and early adolescent adjustment and substance use; and affiliation with substance-using peers. RESULTS: Illicit drug use and abuse/dependence from ages 16 to 25 were significantly associated (all p values<.05) with a range of parental adjustment measures; exposure to abuse in childhood; individual factors; and measures of childhood and early adolescent adjustment. Analyses using repeated measures logistic regression models suggested that parental illicit drug use, gender, novelty-seeking, and childhood conduct disorder predicted later illicit drug use and abuse/dependence. Further analyses revealed that these pathways to illicit drug use and abuse/dependence were mediated via cannabis use, affiliation with substance-using peers, and alcohol use during ages 16-25. CONCLUSIONS: The current study suggested that the illicit drug use and abuse/dependence were associated with a range of early life circumstances and processes that put individuals at greater risk of illicit drug use and abuse/dependence. However, the use of cannabis in late adolescence and early adulthood emerged as the strongest risk factor for later involvement in other illicit drugs.     

'Diagnostic orphans' among young adult cannabis users: persons who report dependence symptoms but do not meet 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. METHOD: Data were collected from a representative population cohort of 1601 young adults aged 20-21 years. 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. RESULTS: Approximately 2.8% of the cohort could be classified as diagnostic orphans, with another 3.0 and 7.5% meeting criteria for abuse and dependence, respectively. Diagnostic orphans were: similar to those who met criteria for cannabis abuse or dependence in terms of demographic characteristics; similar to those who met criteria for cannabis abuse in terms of cannabis use patterns; and similar to those who met criteria for abuse and dependence in their rates of heavy alcohol use and DSM-IV alcohol dependence. However, they did not appear to have elevated rates of illicit drug use or mental health problems compared to non users. CONCLUSIONS: Diagnostic orphans reported using cannabis in a manner similar to persons meeting criteria for cannabis abuse, and had similar rates of alcohol dependence and other illicit drug use. Strict adherence to DSM-IV diagnoses of abuse and dependence may overlook a substantial proportion of young persons who experience cannabis-related problems. There is a need to consider (a) subthreshold levels of cannabis-related problems among those seeking treatment for other problems; and (b) interventions for this group to prevent escalation of such problems.     

Cannabis withdrawal in adolescent treatment seekers

A valid cannabis withdrawal syndrome has been demonstrated in controlled studies with adult marijuana abusers, yet few published reports have examined cannabis withdrawal among adolescents. Adolescents presenting for outpatient substance abuse treatment, whose primary substance of abuse was cannabis, completed a questionnaire reporting the presence and severity of withdrawal symptoms during past periods of cannabis abstinence. Nearly two-thirds of the sample indicated that they had experienced four or more symptoms, and over one-third reported four or more symptoms that occurred at a moderate or greater severity. The magnitude of withdrawal severity was positively correlated with current emotional and behavioral symptoms and self-reported problems with cannabis use. These findings are consistent with previous studies, though the prevalence and magnitude of withdrawal symptoms were lower than that observed in a similar study with adult treatment seekers [Budney, A.J., Novy, P., Hughes, J.R., 1999. Marijuana withdrawal among adults seeking treatment for marijuana dependence. Addiction 94, 1311-1322]. Further research is needed to elucidate associations between cannabis withdrawal effects, the initiation of cessation attempts, and relapse.     

Cannabis withdrawal is common among treatment-seeking adolescents with cannabis dependence and major depression, and is associated with rapid relapse to dependence

Recently, reports have suggested that cannabis withdrawal occurs commonly in adults with cannabis dependence, though it is unclear whether this extends to those with comorbid depression or to comorbid adolescents. We hypothesized that cannabis withdrawal would be common among our sample of comorbid adolescents and young adults, and that the presence of cannabis withdrawal symptoms would be associated with a self-reported past history of rapid reinstatement of cannabis dependence symptoms (rapid relapse). The participants in this study included 170 adolescents and young adults, including 104 with cannabis dependence, 32 with cannabis abuse, and 34 with cannabis use without dependence or abuse. All of these subjects demonstrated current depressive symptoms and cannabis use, and most demonstrated current DSM-IV major depressive disorder and current comorbid cannabis dependence. These subjects had presented for treatment for either of two double-blind, placebo-controlled trials involving fluoxetine. Cannabis withdrawal was the most commonly reported cannabis dependence criterion among the 104 subjects in our sample with cannabis dependence, being noted in 92% of subjects, using a two-symptom cutoff for determination of cannabis withdrawal. The most common withdrawal symptoms among those with cannabis dependence were craving (82%), irritability (76%), restlessness (58%), anxiety (55%), and depression (52%). Cannabis withdrawal symptoms (in the N=170 sample) were reported to have been associated with rapid reinstatement of cannabis dependence symptoms (rapid relapse). These findings suggest that cannabis withdrawal should be included as a diagnosis in the upcoming DSM-V, and should be listed in the upcoming criteria list for the DSM-V diagnostic category of cannabis dependence.     

Functioning of Cannabis Abuse and Dependence Criteria Across Two Different Countries: The United States and The Netherlands

Background: Cross-national differences could affect the likelihood of endorsement of DSM cannabis abuse and dependence criteria. The present study examines whether cannabis abuse and dependence criteria function differently across U.S. and Dutch cannabis users. Method: Data on lifetime endorsement of DSM-IV cannabis abuse/dependence criteria were utilized from U.S. cannabis users who participated in the National Epidemiological Survey on Alcohol and Related Conditions (NESARC) and from Dutch cannabis users who participated in the Zuid-Holland study. In total, 1,568 cannabis users participated in the NESARC sample, and 359 cannabis users participated in the Zuid-Holland sample. The DSM-IV cannabis abuse/dependence criteria as well as cannabis withdrawal were determined using face-to-face computer-assisted personal interviews. Results: Using Restricted Factor Analysis with Latent Moderated Structures, the cannabis abuse/dependence criteria legal problems (β = ?0.43), failed quit attempts (β = ?1.09), use despite problems (β = ?0.32), and withdrawal (β = ?0.53) showed measurement bias, and were more likely to be endorsed by U.S. than by Dutch cannabis users. Also, men were more likely than women to endorse the criteria hazardous use (β = ?0.27), legal problems (β = ?0.49) and tolerance (β = ?0.20). Findings on failed quit attempts and withdrawal were replicated in matched subsamples, while results on legal problems (country and gender) were partly replicated. Conclusions: Several CUD criteria showed measurement bias across two countries and between males and females. Therefore, differences between countries and gender in prevalence rates of CUD should be regarded with caution.     

The influence of cannabis use expectancies on cannabis use and psychotic symptoms in psychosis

Introduction and Aims. Little is known about motives or expectancies for cannabis use in psychotic populations, despite these cognitive factors being a central focus of the treatment for substance misuse in psychosis. This study examined the relationship between cannabis use expectancies, cannabis use and psychotic symptoms among cannabis using psychotic inpatients. A secondary aim was to determine if there were significant differences in the cannabis use expectancies of psychotic patients with and without Diagnostic and Statistical Manual version IV (DSM‐IV) cannabis dependence. Design and Methods. Participants consisted of 101 in‐patients with psychosis who had used cannabis more than five times in the past year. Expectancies were assessed using the Cannabis Expectancy Questionnaire (CEQ). The frequency of cannabis use, severity of cannabis dependence, presence of DSM‐IV cannabis dependence and severity of psychotic symptoms were also assessed using standardised measures. Results and Conclusions. Results suggested that cannabis use expectancies were associated with cannabis use but not symptom variables. Expectances for cannabis use predicted recent cannabis use and the presence and severity of cannabis dependence. Psychotic patients with DSM‐IV cannabis dependence had significantly higher expectancies for negative effects from cannabis use. Prospective research examining the influence of motives and expectancies for cannabis use on cannabis use and psychotic symptoms is required to obtain a greater understanding of substance use in psychosis and assist with the development of innovative treatment interventions.[Hides L, Kavanagh DJ, Dawe S, Young RMcD. The influence of cannabis use expectancies on cannabis use and psychotic symptoms in psychosis. Drug Alcohol Rev 2009;28:250–256]     

Tri-city study of Ecstasy use problems: a latent class analysis

This study used latent class analysis to examine distinctive subtypes of Ecstasy users based on 24 abuse and dependence symptoms underlying standard DSM-IV criteria. Data came from a three site, population-based, epidemiological study to examine diagnostic nosology for Ecstasy use. Subject inclusion criteria included lifetime Ecstasy use exceeding five times and once in the past year, with participants ranging in age between 16 and 47 years of age from St. Louis, Miami, U.S. and Sydney, Australia. A satisfactory model typified four latent classes representing clearly differentiated diagnostic clusters including: (1) a group of sub-threshold users endorsing few abuse and dependence symptoms (negatives), (2) a group of 'diagnostic orphans' who had characteristic features of dependence for a select group of symptoms (mild dependent), (3) a 'transitional group' mimicking the orphans with regard to their profile of dependence also but reporting some abuse symptoms (moderate dependent), and (4) a 'severe dependent' group with a distinct profile of abuse and dependence symptoms. A multinomial logistic regression model indicated that certain latent classes showed unique associations with external non-diagnostic markers. Controlling for demographic characteristics and lifetime quantity of Ecstasy pill use, criminal behavior and motivational cues for Ecstasy use were the most efficient predictors of cluster membership. This study reinforces the heuristic utility of DSM-IV criteria applied to Ecstasy but with a different collage of symptoms that produced four distinct classes of Ecstasy users.     

What predicts incident use of cannabis and progression to abuse and dependence? A 4-year prospective examination of risk factors in a community sample of adolescents and young adults

OBJECTIVES: To determine risk factors of incident onset of use, abuse and dependence of cannabis in a community sample of adolescents and young adults. METHODS: Risk factors were examined in a prospective longitudinal design across 4 years in a representative sample (N = 2,446) aged 14-24 at the outset of the study (EDSP). Patterns of DSM-IV defined cannabis use, abuse and dependence were assessed with the Composite International Diagnostic Interview (M-CIDI). Potential risk factors were assessed at baseline. Incident cannabis use, abuse and dependence at second follow-up (on average 42 months after baseline) were the main outcome measures in this study. Associations were analyzed with logistic and negative binomial regressions. RESULTS: Using 11 of a total of 56 variables examined, the predictive value of the final multiple logistic regression for incident cannabis use was moderately good (area under the ROC curve = 0.78). Cannabis use frequency was predicted in the final model by 18 variables, cannabis abuse by two variables in the younger subsample and nine factors in the older group, and dependence by eight variables (dependence: ROC curve area = 0.97). Incident cannabis use was predicted mainly by availability of drugs, peers' drug use, a more 'positive' attitude towards future drug use, and regular previous use of licit drugs, while cannabis dependence was predicted primarily by parental death before age 15, deprived socio-economic status, and baseline use of other illicit drugs. CONCLUSION: Different factors predict the onset or severity of cannabis use and the progression to abuse and dependence. In addition to well-documented risk factors such as peer group pressure, drug availability, and low self-esteem, findings suggest that family history (e.g. parental mental disorders, early parental death), and prior experiences with legal drugs play a significant role in the initiation of cannabis consumption and the transition to cannabis use disorders in adolescents and young adults. Findings suggest that early intervention and prevention might be improved by better targeted treatment.