Marijuana use from adolescence to adulthood: developmental trajectories and their outcomes.

BACKGROUND: The study assesses the degree to which individuals in different trajectories of marijuana use are similar or different in terms of unconventional behavior, sensation seeking, emotional dysregulation, nicotine dependence, alcohol dependence/abuse, children living at home, and spouse/partner marijuana use at age 43. METHOD: This study used a longitudinal design. The sample participants (N = 548) were first studied at mean age 14 and last studied at mean age 43. RESULTS: Six trajectories of marijuana use were identified: chronic/heavy users (3.6 %), increasing users (5.1 %), chronic/occasional users (20 %), decreasers (14.3 %), quitters (22.5 %), and nonusers/experimenters (34.5 %). With three exceptions, as compared with being a nonuser/experimenter, a higher probability of belonging to the chronic/heavy, the increasing, or the chronic/occasional user trajectory group was significantly associated with a greater likelihood of unconventional behavior, sensation seeking, emotional dysregulation, nicotine dependence, alcohol dependence/abuse, not having children who lived at home, and having a spouse/partner who used marijuana at early midlife. In addition, compared with being a quitter, a higher probability of belonging to the chronic/heavy user trajectory group was significantly associated with a higher likelihood of unconventional behavior, sensation seeking, emotional dysregulation, alcohol dependence/abuse, and spouse/partner marijuana use. Implications for intervention are presented. CONCLUSIONS: Trajectories of marijuana use, especially chronic/heavy use, increasing use, and chronic/occasional use, are associated with unconventional behavior, sensation seeking, emotional dysregulation, nicotine dependence, alcohol dependence/abuse, having children who lived at home, and spouse/partner marijuana use at age 43. The importance of the findings for prevention and treatment programs are discussed.

Examining the profile of high-potency cannabis and its association with severity of cannabis dependence.

BACKGROUND: Cannabis use is decreasing in England and Wales, while demand for cannabis treatment in addiction services continues to rise. This could be partly due to an increased availability of high-potency cannabis. METHOD: Adults residing in the UK were questioned about their drug use, including three types of cannabis (high potency: skunk; low potency: other grass, resin). Cannabis types were profiled and examined for possible associations between frequency of use and (i) cannabis dependence, (ii) cannabis-related concerns. RESULTS: Frequent use of high-potency cannabis predicted a greater severity of dependence [days of skunk use per month: b = 0.254, 95% confidence interval (CI) 0.161-0.357, p < 0.001] and this effect became stronger as age decreased (b = -0.006, 95% CI -0.010 to -0.002, p = 0.004). By contrast, use of low-potency cannabis was not associated with dependence (days of other grass use per month: b = 0.020, 95% CI -0.029 to 0.070, p = 0.436; days of resin use per month: b = 0.025, 95% CI -0.019 to 0.067, p = 0.245). Frequency of cannabis use (all types) did not predict severity of cannabis-related concerns. High-potency cannabis was clearly distinct from low-potency varieties by its marked effects on memory and paranoia. It also produced the best high, was preferred, and most available. CONCLUSIONS: High-potency cannabis use is associated with an increased severity of dependence, especially in young people. Its profile is strongly defined by negative effects (memory, paranoia), but also positive characteristics (best high, preferred type), which may be important when considering clinical or public health interventions focusing on cannabis potency.

Typology of individuals with substance dependence based on a Montreal longitudinal catchment area study.

This study sought to develop a typology of individuals with substance dependence (ISD) based on a longitudinal survey (n = 2,434) and 121 ISD. The latter were divided into three groups: newly abstinent individuals, chronic dependents and acute dependents. Individuals' typology was developed by cluster analysis. Newly abstinent individuals had fewer emotional problems and mental disorders in the previous 12 months. Four classes of ISD were identified, labelled respectively "chronic multi-substance consumption and mental disorders comorbidities," "multi-substance consumption," "alcohol and marijuana consumption" and "alcohol consumption only." Strategies adapted to each of these profiles could be promoted for more effective treatment.

Developmental trajectories of marijuana use from adolescence to adulthood: relationship with using weapons including guns.

This is the first study to assess the associations between the trajectories of marijuana use and other predictors of violent behavior with the use of guns or other weapons as well as stealing without the use of weapons among inner-city African Americans and Puerto Ricans (N = 838). Logistic regression analyses examined whether the longitudinal trajectories of marijuana use compared with the trajectory of no/low marijuana use predicted violent behavior. A higher Bayesian posterior probability (BPP) for the increasing marijuana use trajectory group (AOR = 3.37, P < .001), the moderate use of marijuana trajectory group (AOR = 1.98, P < .01), and the quitter trajectory group (AOR = 1.70, P < .05) was associated with an increased likelihood of engaging in violence (i.e., shooting or hitting someone with a weapon) compared with the BPP of the no use of marijuana trajectory group. Our results address a number of important public health and clinical issues. Public health funds might be spent on prevention programs focused on decreasing the use of marijuana, increasing educational retention, and decreasing contact with deviant associates. Understanding the psychosocial conditions related to the use of weapons is critical for individuals involved in the criminal justice system, physicians, and other health care providers in managing individuals who engage in violent behavior.

An assessment of the compatibility of DSM-IV and proposed DSM-5 criteria in the diagnosis of cannabis use disorders.

The current study used an automated version of the substance use disorder diagnostic schedule-IV (SUDDS-IV) to assess DSM-IV (fourth edition of the Diagnostic and statistical manual of mental disorders) and two sets of proposed DSM-5 (fifth edition of the Diagnostic and statistical manual of mental disorders) cannabis use disorder criteria among adult prison inmates in the Minnesota Department of Corrections state prison system from 2000 to 2003. Initially proposed DSM-5 criteria had only two diagnostic designations (moderate and severe). A subsequent revision added a mild designation and required a greater number of positive findings for the severe diagnosis. The sample was composed of 7,672 (89.6% male) inmates. Inmates with no DSM-IV diagnoses and most who currently received a cannabis dependence diagnosis according to the DSM-IV guidelines will fit into corresponding DSM-5 categories (i.e., no diagnosis and severe cannabis use disorder, respectively). Some diagnostic criteria, in addition to those proposed for the DSM-5, emerged as cardinal indicators of moderate cannabis use disorder. The study's limitations are noted.

The classification of Spanish adolescents based on substance consumption patterns and the analysis of the relationships within their social developmental contexts.

This research is part of the 2006 edition of the Health Behavior in School-aged Children (HBSC) study. The data presented were composed of a sample of 15942 Spanish adolescents ranging from 13 to 18 years of age. The instruments used included a variety of questions related to substance consumption among adolescents, their bio-psycho-social adjustment and developmental contexts, all of which are part of the HBSC study instrument bank. Through classification analysis, as well as significance and effect size tests, we obtained relevant information about the current epidemiology of substance consumption among Spanish adolescents. These results are representative of the Spanish adolescent population which allows the typical risk profile attributed to young people to be clarified. A gradual adjustment can be seen in terms of substance consumption levels in youth and that same level in their friends. Likewise, the analysis of the developmental context (family, friends and school) provides important information when it comes to preventing substance consumption, thus showing the advantages that coherence and connection have between the different environments where youth live, grow up and develop.

Complex cannabis use patterns: Associations with cannabis consequences and cannabis use disorder symptomatology.

BACKGROUND: Historically, cannabis researchers have assumed a single mode and product of cannabis (e.g., smoking plant). However, patterns of use, products (e.g., concentrates, edibles), and modes (e.g. blunts, vaporizers) are diversifying. This study sought to: 1) classify cannabis users into groups based on their use of the full range of cannabis products, and 2) examine user group differences on demographics, cannabis consequences and cannabis use disorder (CUD) symptomatology. METHODS: In a sample of college students (data collected in Fall 2017), who used cannabis in the past year (N = 1390), latent class analysis (LCA) was used to characterize cannabis users. We then added demographic characteristics, cannabis consequences, and CUD symptomatology scores separately to LCA models to examine class differences. RESULTS: Five unique classes emerged: high-frequency all-product users, high-frequency plant/moderate-frequency edible and concentrate users, low-frequency plant users, moderate-frequency plant and edible users, and low-frequency edible users. Demographic characteristics, cannabis consequences, and CUD symptomatology differed across classes characterized by frequency as well as product. CONCLUSIONS: Results reflect the increasing variety of cannabis products, modes, and use patterns among college students. In this sample, frequency of use remains a strong predictor of cannabis-related consequences, in addition to type of product. As variation in cannabis use patterns continue to evolve, it is essential for researchers to conduct comprehensive assessments.

Heritability and a genome-wide linkage analysis of a Type II/B cluster construct for cannabis dependence in an American Indian community.

Subtyping of substance dependence disorders holds promise for a number of important research areas including phenotyping for genetic studies, characterizing clinical course, and matching treatment and prevention strategies. This study sought to investigate whether a dichotomous construct similar to Babor's Types A/B and Cloninger's Types I/II for alcohol dependence can be identified for cannabis dependence in a Native American sample. In addition, heritability of this construct and its behavior in a genetic linkage analyses were evaluated. Information on cannabis use and dependence symptoms and other psychiatric disorders was obtained using the Semi-Structured Assessment for the Genetics of Alcoholism from a community sample of 606 American Indians. Hierarchical average linkage and K means cluster analysis was used, and a three-cluster solution was found to generate the best separation of variables. Ninety-one per cent of cannabis-dependent participants fell into one of the two subtypes: Type A/I cluster (n = 114, 56%) and Type B/II cluster (n = 70, 35%). Heritability (estimated using Sequential Oligogenic Linkage Analysis Routines) was only significant for the Type B/II cluster (h(2) = 0.44, SE = 0.18, P < 0.01). Evidence for linkage was found for the Type B/II cluster (versus no diagnosis) on chromosome 16 [at 139 centimorgans (cM), Log of the Odds (LOD) score = 4.4], and on chromosome 19 (at 74 cM, LOD score = 6.4). Regions of interest for this phenotype (LOD > 1.5) were also located on chromosomes 14, 21, 22. These findings suggest that a Type B/II cannabis dependence phenotype can be identified in this population and that it is in part heritable and linked to areas of the genome identified previously for drug dependence phenotypes in this population as well as in other studies.

Concordance between the diagnostic guidelines for alcohol and cannabis use disorders in the draft ICD-11 and other classification systems: analysis of data from the WHO's World Mental Health Surveys.

BACKGROUND AND AIMS: The World Health Organization's (WHO's) proposed International Classification of Diseases, 11th edition (ICD-11) includes several major revisions to substance use disorder (SUD) diagnoses. It is essential to ensure the consistency of within-subject diagnostic findings throughout countries, languages and cultures. To date, agreement analyses between different SUD diagnostic systems have largely been based in high-income countries and clinical samples rather than general population samples. We aimed to evaluate the prevalence of, and concordance between diagnoses using the ICD-11, The WHO's ICD 10th edition (ICD-10) and the Diagnostic and Statistical Manual of Mental Disorders, 4th and 5th editions (DSM-IV, DSM-5); the prevalence of disaggregated ICD-10 and ICD-11 symptoms; and variation in clinical features across diagnostic groups. DESIGN: Cross-sectional household surveys. SETTING: Representative surveys of the general population in 10 countries (Argentina, Australia, Brazil, Colombia, Iraq, Northern Ireland, Poland, Portugal, Romania and Spain) of the World Mental Health Survey Initiative. PARTICIPANTS: Questions about SUDs were asked of 12 182 regular alcohol users and 1788 cannabis users. MEASUREMENTS: Each survey used the World Mental Health Survey Initiative version of the WHO Composite International Diagnostic Interview version 3.0 (WMH-CIDI). FINDINGS: Among regular alcohol users, prevalence (95% confidence interval) of life-time ICD-11 alcohol harmful use and dependence were 21.6% (20.5-22.6%) and 7.0% (6.4-7.7%), respectively. Among cannabis users, 9.3% (7.4-11.1%) met criteria for ICD-11 harmful use and 3.2% (2.3-4.0%) for dependence. For both substances, all comparisons of ICD-11 with ICD-10 and DSM-IV showed excellent concordance (all κ ≥ 0.9). Concordance between ICD-11 and DSM-5 ranged from good (for SUD and comparisons of dependence and severe SUD) to poor (for comparisons of harmful use and mild SUD). Very low endorsement rates were observed for new ICD-11 feature for harmful use ('harm to others'). Minimal variation in clinical features was observed across diagnostic systems. CONCLUSIONS: The World Health Organization's proposed International Classification of Diseases, 11th edition (ICD-11) classifications for substance use disorder diagnoses are highly consistent with the ICD 10th edition and the Diagnostic and Statistical Manual of Mental Disorders, 4th edition (DSM-IV). Concordance between ICD-11 and the DSM 5th edition (DSM-5) varies, due largely to low levels of agreement for the ICD harmful use and DSM-5 mild use disorder. Diagnostic validity of self-reported 'harm to others' is questionable.

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.

Client matching: a severity-treatment intensity paradigm.

Despite considerable effort to develop matching strategies and client placement protocols, research studies fail to yield compelling results regarding the benefits of matching to treatment. The most consistent findings suggest a matching paradigm, which defines a successful placement as the least treatment intensity required addressing the severity of the disorder. The purpose of the present study is to provide further empirical support for the validity of a severity-intensity paradigm utilizing data from the Drug Abuse Treatment Outcome Studies. A "passive match" approach employed the Client Matching Protocol decision algorithm, which recommended clients to long-term residential or outpatient drug-free treatment. One-year outcomes for clients matched to long-term residential treatment were better on all outcome variables compared to those undertreated in outpatient drug-free treatment. Findings supported the validity of the severity-intensity paradigm in that undertreated clients showed less improvement compared to matched and overtreated clients.

A comparison of the latent class structure of cannabis problems among adult men and women who have used cannabis repeatedly.

BACKGROUND: Little empirical evidence exists to determine if there are alternative classification schemes for cannabis abuse and dependence beyond the definitions provided by Diagnostic and Statistical Manual (DSM) criteria. Current evidence is not conclusive regarding gender differences for cannabis use, abuse and dependence. It is not known if symptom profiles differ by gender. METHODS: Latent class analysis (LCA) was used to assess whether cannabis abuse and dependence symptom patterns suggest a severity spectrum or distinct subtypes and to test whether symptom patterns differ by gender. Data from 3312 men and 2509 women in the National Longitudinal Alcohol Epidemiologic Survey (NLAES) who had used cannabis 12 + times life-time were included in the present analyses. The comparability of the solutions for men and women was examined through likelihood ratio chi(2) tests. RESULTS: Based on the Bayesian information criterion and interpretability, a four-class solution was selected, and the classes were labeled as 'unaffected/mild hazardous use', 'hazardous use/abuse', 'abuse/moderate dependence' and 'severe abuse/dependence'. The solutions were generally suggestive of a severity spectrum. Compared to men, women were more likely to be in the 'unaffected/mild hazardous use' class and less likely to be in the 'abuse/moderate dependence' or 'severe abuse/dependence' classes. The results were generally similar for men and women. However, men had consistently and substantially higher endorsements of hazardous use than women, women in the 'abuse/moderate dependence' class had moderately higher rates for four dependence symptoms, and women in two of the classes were more likely to endorse withdrawal. CONCLUSION: Our findings generally support the severity dimension for DSM-IV cannabis abuse and dependence symptomatology for both men and women. While our results indicate that public health messages may have generic and not gender-specific content, treatment providers should focus more effort on reducing hazardous use in men and alleviating withdrawal in women.

The Severity of Dependence Scale (SDS) in an adolescent population of cannabis users: reliability, validity and diagnostic cut-off.

The Severity of Dependence Scale (SDS) is a five-item scale that has been reported to be a reliable and valid screening instrument for dependence and a measure of dependence severity in adults across several substance classes. To date no data have been reported on its performance in a population of adolescent cannabis users. The current study assessed the psychometric properties of the SDS in a community sample of 14-18-year-old adolescent cannabis users (n=100). Internal consistency (alpha=0.83) and test-retest coefficients (ICC=0.88) were high and a principal components analysis of the scale found all items to load on a single factor. Total SDS score correlated significantly with frequency of cannabis use and number of DSM-IV dependence criteria met, indicating good concurrent validity. Receiver Operating Characteristic curve analysis was used to determine the most appropriate SDS cut-off score for use as an indicator of cannabis dependence, with optimal discrimination at an SDS score of 4. These findings indicate that the SDS is a reliable and valid measure of severity of cannabis dependence among adolescents, has high diagnostic utility, and that an SDS score of 4 may be indicative of cannabis dependence.

Concordance of ICD-11 and DSM-5 definitions of alcohol and cannabis use disorders: a population survey.

The proposed criteria for alcohol and cannabis use disorders in the 11th edition of ICD (ICD-11) will be presented to the World Health Assembly in 2017, but the beta-phase descriptions have been released. We compared them with those in the tenth edition (ICD-10) and the American Psychiatric Association's DSM fourth edition (DSM-IV) and fifth edition (DSM-5), in a nationally representative sample of adult Australians. Disorders were assessed with the WHO World Mental Health Composite International Diagnostic Interview. The proportions classified as being dependent on alcohol and cannabis were similar with ICD-10, ICD-11, and DSM-IV, whereas for DSM-5, the proportion of lifetime users meeting the criteria for moderate to severe use (most comparable to dependence in the other systems) was far higher. We assessed whether criteria for alcohol and cannabis use described unidimensional syndromes for each, and all definitions seemed to do so. Classification of alcohol and cannabis use disorders, although simplified in ICD-11, was in almost perfect agreement with the classifications of ICD-10 and DSM-IV. With DSM-5, use disorder seemed to capture a different aspect of problematic use and selected a different group of individuals from the other systems. How the newest definitions will become used remains to be seen. The choice of classification might depend on the clinical population of interest.

Genome-wide Association Study of Cannabis Dependence Severity, Novel Risk Variants, and Shared Genetic Risks.

IMPORTANCE: Cannabis dependence (CAD) is a serious problem worldwide and is of growing importance in the United States because cannabis is increasingly available legally. Although genetic factors contribute substantially to CAD risk, at present no well-established specific genetic risk factors for CAD have been elucidated. OBJECTIVE: To report findings for DSM-IV CAD criteria from association analyses performed in large cohorts of African American and European American participants from 3 studies of substance use disorder genetics. DESIGN, SETTING, AND PARTICIPANTS: This genome-wide association study for DSM-IV CAD criterion count was performed in 3 independent substance dependence cohorts (the Yale-Penn Study, Study of Addiction: Genetics and Environment [SAGE], and International Consortium on the Genetics of Heroin Dependence [ICGHD]). A referral sample and volunteers recruited in the community and from substance abuse treatment centers included 6000 African American and 8754 European American participants, including some from small families. Participants from the Yale-Penn Study were recruited from 2000 to 2013. Data were collected for the SAGE trial from 1990 to 2007 and for the ICGHD from 2004 to 2009. Data were analyzed from January 2, 2013, to November 9, 2015. MAIN OUTCOMES AND MEASURES: Criterion count for DSM-IV CAD. RESULTS: Among the 14 754 participants, 7879 were male, 6875 were female, and the mean (SD) age was 39.2 (10.2) years. Three independent regions with genome-wide significant single-nucleotide polymorphism associations were identified, considering the largest possible sample. These included rs143244591 (ß = 0.54, P = 4.32 × 10-10 for the meta-analysis) in novel antisense transcript RP11-206M11.7;rs146091982 (ß = 0.54, P = 1.33 × 10-9 for the meta-analysis) in the solute carrier family 35 member G1 gene (SLC35G1); and rs77378271 (ß = 0.29, P = 2.13 × 10-8 for the meta-analysis) in the CUB and Sushi multiple domains 1 gene (CSMD1). Also noted was evidence of genome-level pleiotropy between CAD and major depressive disorder and for an association with single-nucleotide polymorphisms in genes associated with schizophrenia risk. Several of the genes identified have functions related to neuronal calcium homeostasis or central nervous system development. CONCLUSIONS AND RELEVANCE: These results are the first, to our knowledge, to identify specific CAD risk alleles and potential genetic factors contributing to the comorbidity of CAD with major depression and schizophrenia.

Identifying classes of conjoint alcohol and marijuana use in entering freshmen.

The current study identified classes of conjoint marijuana and alcohol use in entering college freshmen using latent profile analysis (N = 772; 53% male, 60% White; Mage = 18). Results yielded 4 distinct groups: Class 1 (moderate drinking with recent marijuana use: 22% of sample), Class 2 (moderate drinking with no recent marijuana use: 25%), Class 3 (light drinking with no recent marijuana use: 40%) and Class 4 (heavy drinking with recent marijuana use: 14%). Separate pairwise contrasts examined cross-class differences in demographics and drinking behaviors, comparing differences in drinking when current marijuana use was controlled (Class 1 vs. 4) and differences in marijuana use when drinking was held relatively constant (Class 1 vs. 2). Among moderate drinkers, recent marijuana users were more likely to drink more than intended, drink to get drunk, and had more problems (including higher rates of blackouts, physical injury, and DUI) relative to peers who refrained from marijuana. No cross-class differences were found for alcohol expectancies or behavioral motives. Findings from these analyses show the presence of distinct groups of conjoint users with different drinking behaviors and consequence profiles, and suggest that conjoint alcohol-marijuana use may be more problematic overall than single substance involvement and highlight the need for developing campus prevention and intervention programs that address the increased risk from polysubstance involvement.

The deficit syndrome in the DSM-IV Field Trial: I. Alcohol and other drug abuse.

Drug abuse is common in schizophrenia. Previous studies suggested patients with the deficit syndrome have a lower risk of drug abuse than do patients without deficit features. We distinguished deficit and nondeficit groups in the DSM-IV Field Trial dataset, and compared the two groups relative to current and lifetime (worst ever) severity of alcohol, cannabis, and other drugs of abuse. Deficit syndrome patients had a lower severity of current use of alcohol and other drugs, but the two groups did not differ significantly relative to cannabis use. Deficit patients also had less severe lifetime use of all three classes of drugs. These findings could not be attributed to differences between the deficit and nondeficit groups in demographics, severity of psychotic symptoms, chronicity of illness, or the quality of information available for the two groups. Deficit categorization and drug abuse were independently associated with poor level of function. Negative symptoms broadly defined were weaker predictors of drug abuse than was the deficit/nondeficit categorization. These findings further support the validity of the deficit syndrome of schizophrenia. Within schizophrenia, groups with relatively high or low risk for substance abuse can be identified.

Subtypes for classifying adolescents with marijuana use disorders: construct validity and clinical implications.

AIMS: To evaluate the construct and predictive validity of six different subtyping classifications selected on the basis of their empirical support in the literature on adolescent substance abuse. METHODS: Typological data were collected from a heterogeneous sample of 600 adolescents presenting for marijuana treatment. The classification schemes were gender, onset age, family history, externalizing disorders, internalizing disorders and temperament. Subgroups were compared in terms of substance use frequency, substance abuse problems, social support for substance use, family conflict, school problems and negative peer associations. RESULTS: Each of the categorical classification schemes differentiated subtypes significantly on some or all of the construct validation measures after controlling for demographic factors, thereby indicating that each has valuable explanatory power from a theoretical perspective. Externalizing disorders, onset age, difficult temperament and internalizing disorders continued to add unique variance to discrimination after the effects of the other subtypes had been removed. At 12-month follow-up there were no differences between subtypes on substance use frequency, but adolescents with higher levels of externalizing disorders and internalizing disorders continued to experience more substance use problems. CONCLUSION: Categorical subtypes may have particular relevance to the development of treatment interventions as well as prevention measures.

Characteristics of DSM-IV and ICD-10 cannabis dependence among Australian adults: results from the National Survey of Mental Health and Wellbeing.

A representative sample (n = 10641) of Australian adults completed a structured diagnostic interview assessing the prevalence of mental and substance use disorders in the last year. The prevalence of DSM-IV (1.5%) and ICD-10 (1.7%) cannabis dependence was similar. DSM-IV and ICD-10 dependence criteria comprised unidimensional syndromes. The most common symptoms among dependent and non-dependent users were difficulties with controlling use and withdrawal, although there were marked differences in symptom prevalence. Dependent users reported a median of four symptoms. There was good to excellent diagnostic concordance (kappas = 0.7-0.9) between systems for dependence but not for abuse/harmful use (Y = 0.4). These findings provide some support for the validity of cannabis dependence.

Relationships between frequency and quantity of marijuana use and last year proxy dependence among adolescents and adults in the United States.

The association between levels of marijuana use and last year dependence is investigated in a nationally representative sample of adolescents and adults, who used marijuana within the last year (n = 9284). Data are aggregated from three surveys (1991-1993) of the National Household Survey on Drug Abuse. A proxy measure of DSM-IV dependence criteria was developed from self-reported symptoms of dependence and drug-related problems. Both frequency and quantity of marijuana use within the last year are linearly associated with the logit of the probability of being dependent on marijuana. The associations vary significantly by age but not gender. Adolescents are dependent at a lower frequency and quantity of use than adults: the differences diverge as level of use increases. Twice as many adolescents as adults who used marijuana near-daily or daily within the last year were identified as being dependent (35% versus 18%). Frequency and quantity of use each retained a unique effect on dependence, but frequency appeared to be more important than quantity in predicting last year dependence. These results provide insight into the processes underlying the age and sex differentials observed in the prevalence of marijuana dependence. The implications of the findings for the epidemiology of marijuana use and dependence are discussed.