Cannabis use disorder is defined by patterns of use that cause clinically significant psychiatric distress (e.g. depression, anxiety, irritability, psychosis) and social impairment (e.g., the loss of relationship ties, financial difficulties, legal problems), and which are associated with repeated failed attempts to stop using it. Cannabis use disorder is often coupled with tobacco use, and there is evidence for the two substances having a synergetic effect on dependence.
Epidemiological studies estimate that around 1 in every 6 teenager users and 1 in every 2 daily cannabis users will meet the criteria for cannabis dependence at some point in the future. In the U.S., the lifetime rate of cannabis use disorder is 6.3% whereas in Australia it is 5.4%. Demand for professional health assistance is increasing globally, and without effective pharmacotherapies to this day, psychosocial treatments are the only alternative.
The most common psychosocial therapies fall under the umbrella of cognitive-behavioral and motivational enhancement approaches. The first focuses on relapse prevention via identification and management of patterns, thoughts, and external triggers that lead to use, as well as teaching coping, problem-solving skills, and promoting healthier substitutes. The second has a more general focus on building motivation, feelings of self-efficacy, and positive changes. Besides these two, secondary interventions include mindfulness meditation and drug education, and on top of these, health practitioners have tried pharmacological medication, smoke management, and financial incentives for abstinence or engagement in treatment.
The effectiveness of these therapies on cannabis use disorder is questionable, given that previous meta-analyses were restricted to very small samples. In an attempt to solve this issue, a new systematic review was conducted by Australian and Canadian researchers, under the auspices of the Cochrane Collaboration.
Twenty-three randomized and controlled studies encompassing more than 4000 participants were selected for the final analysis. The majority were conducted in the United States, whereas only one was from Canada. The authors found that 7 out of every 10 participants completed intervention as planned, and judged the evidence that psychosocial interventions promote a reduction in days of cannabis use to be of “moderate-quality.” Weaker evidence suggested that interventions also reduced symptoms of dependence and cannabis-related problems, whereas only “very low-quality” evidence indicated a reduction in the number of joints per day among those who received intervention.
A more refined analysis suggested that interventions of more than four sessions lasting for over a month led to better outcomes in the short term (6 months) compared to less intense interventions. The strongest evidence was provided by cognitive-behavioral therapies, motivational enhancement therapies, or a combination of both. In addition to these, voucher-based incentives for negative urine tests seemed to enhance the effect of therapies on cannabis use frequency. Evidence for the remaining interventions was missing or, at best, inconclusive. Importantly, there was no consistent evidence for therapeutic effects lasting for nine months or more.
While a positive picture emerged from the reviewed studies, some issues remain to be answered. There is no consensus on how concurrent tobacco use should be addressed, despite knowing that it aggravates this disorder. It is also still unclear to what extent some of the problems of cannabis use disorder are related to the legal consequences of its use and not to the substance itself. Finally, evidence that psychosocial interventions work for those people who are not actively seeking them is still missing.