Wendy Swift

A randomized controlled trial of brief cognitive-behavioral interventions for cannabis use disorder.

The increasing demand for treatment for cannabis dependence in Australia and internationally has led to the identification of significant gaps in knowledge of effective interventions. A randomized controlled trial of brief cognitive-behavioral interventions (CBT) for cannabis dependence was undertaken to address this issue. A total of 229 participants were assessed and randomly assigned to either a six-session CBT program (6CBT), a single-session CBT intervention (1CBT), or a delayed-treatment control (DTC) group. Participants were assisted in acquiring skills to promote cannabis cessation and maintenance of abstinence. Participants were followed-up a median of 237 days after last attendance. Participants in the treatment groups reported better treatment outcomes than the DTC group. They were more likely to report abstinence, were significantly less concerned about their control over cannabis use, and reported significantly fewer cannabis-related problems than those in the DTC group. Those in the 6CBT group also reported more significantly reduced levels of cannabis consumption than the DTC group. While the therapist variable had no effect on any outcome, a secondary analysis of the 6CBT and 1CBT groups showed that treatment compliance was significantly associated with decreased dependence and cannabis-related problems. This study supports the attractiveness and effectiveness of individual CBT interventions for cannabis use disorders and the need for multisite replication trials.

Clinical profile of participants in a brief intervention program for cannabis use disorder

The increasing demand for cannabis dependence treatment has led to the identification of significant gaps in the knowledge of effective interventions. A randomized controlled trial of brief cognitive-behavioral interventions (CBT) for cannabis dependence was undertaken to address this issue. A total of 229 participants were assessed and allocated to either a 6-session CBT program, a single-session brief intervention, or a delayed-treatment control group. This paper demonstrates that individuals with cannabis use disorder will present for a brief intervention program. While they report similar patterns of cannabis use to nontreatment samples, they report a range of serious health and psychosocial consequences. While they appear relatively socially stable, they typically demonstrated severe cannabis dependence and significantly elevated levels of psychological distress, with the most commonly cited reason for cannabis use being stress relief. There were clinically relevant gender differences among the sample. This study provides more evidence of the demand for, and nature of issues relevant to, interventions for cannabis use disorders, and supports the need for further research into how best to assist individuals with these disorders.

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

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

Cannabis potency and contamination: a review of the literature

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

Cannabis use disorder: Epidemiology and management

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

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

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

Drug use, HIV risk-taking and psychosocial correlates of benzodiazepine use among methadone maintenance clients

Methadone maintenance clients who used benzodiazepines were compared with other methadone maintenance clients on a range of drug use and psychosocial treatment outcome measures. Despite being on higher methadone doses, benzodiazepine users were more likely to have recently injected, to have used cocaine and amphetamines, to have borrowed or lent used needles and syringes, and to have reported polydrug use in the preceding month. Benzodiazepine users also exhibited higher levels of psychopathology and social dysfunction than other methadone maintenance clients. It is concluded that benzodiazepine-using methadone maintenance clients are a dysfunctional subgroup of the methadone population, who may require more clinical intervention than other clients.

Analysis of cannabis seizures in NSW, Australia: cannabis potency and cannabinoid profile.

Recent analysis of the cannabinoid content of cannabis plants suggests a shift towards use of high potency plant material with high levels of Δ9-tetrahydrocannabinol (THC) and low levels of other phytocannabinoids, particularly cannabidiol (CBD). Use of this type of cannabis is thought by some to predispose to greater adverse outcomes on mental health and fewer therapeutic benefits. Australia has one of the highest per capita rates of cannabis use in the world yet there has been no previous systematic analysis of the cannabis being used. In the present study we examined the cannabinoid content of 206 cannabis samples that had been confiscated by police from recreational users holding 15 g of cannabis or less, under the New South Wales “Cannabis Cautioning” scheme. A further 26 “Known Provenance” samples were analysed that had been seized by police from larger indoor or outdoor cultivation sites rather than from street level users. An HPLC method was used to determine the content of 9 cannabinoids: THC, CBD, cannabigerol (CBG), and their plant-based carboxylic acid precursors THC-A, CBD-A and CBG-A, as well as cannabichromene (CBC), cannabinol (CBN) and tetrahydrocannabivarin (THC-V). The “Cannabis Cautioning” samples showed high mean THC content (THC+THC-A = 14.88%) and low mean CBD content (CBD+CBD-A = 0.14%). A modest level of CBG was detected (CBG+CBG-A = 1.18%) and very low levels of CBC, CBN and THC-V (<0.1%). “Known Provenance” samples showed no significant differences in THC content between those seized from indoor versus outdoor cultivation sites. The present analysis echoes trends reported in other countries towards the use of high potency cannabis with very low CBD content. The implications for public health outcomes and harm reduction strategies are discussed.

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

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

One year follow-up of cannabis dependence among long-term users in Sydney, Australia

Eighty one percent of a sample of long-term cannabis users was followed up at 1 year (162/200). Half (51%) were daily smokers, while 20% had substantially decreased or ceased use. More than half received a dependence diagnosis on each of three measures in the last year, with 44% dependent on all three. Remission was much more common than incidence of dependence. Nevertheless, use and dependence patterns were strongly related over time. Longitudinal analyses revealed that quantity of use and severity of dependence at baseline were the primary predictors of those same variables at follow-up. These data suggest that cannabis use and dependence are fairly stable among long-term users.