Psychosocial interventions to reduce cannabis use and improve psychosocial functioning

Behavioural therapies (including cognitive behavioural therapies (CBT), motivational interviewing (MI) and contingency management) were found in a systematic review with meta-analysis (Gates et al., 2016, 23 RCTs, N=4 045) to be more effective than control conditions on:

• completing of treatment (effect size (ES) 0.71, 95 % CI 0.63 to 0.78, 11 studies, N=1 424)
• reducing use (MD 5.67, 95 % CI 3.08 to 8.26, six studies, N=1 144)
• improving abstinence (RR 2.55, 95 % CI 1.34 to 4.83, six studies, N=1 166)
• reducing symptoms of dependence (standardised mean difference (SMD) 4.15, 95 % CI 1.67 to 6.63, four studies, N=889)
• reducing cannabis-related problems (SMD 3.34, 95 % CI 1.26 to 5.42, six studies, N=2 202)

The same meta-analysis also found that:

• Interventions of more than four sessions delivered over longer than one month (high intensity) produced consistently improved outcomes (particularly in terms of cannabis use frequency and severity of dependence) in the short term as compared with low-intensity interventions
• The most consistent evidence supports the use of cognitive-behavioural therapy (CBT), motivational enhancement therapy (MET) and particularly their combination for assisting with reduction of cannabis use frequency and severity of dependence at early follow-up
• Data from five out of six studies supported the utility of adding voucher-based incentives for cannabis-negative urines to enhance treatment effect on cannabis use frequency

Evidence of drug counselling, social support, relapse prevention and mindfulness meditation was weak because identified studies were few, information on treatment outcomes insufficient and rates of treatment adherence low.

Behavioural therapies targeting specifically adolescents were analysed in a systematic review without meta-analysis (Hogue et al., 2014, 8 RCTs) arriving at the same conclusions: see comment for the rest of the text

• CBT is well established but was outperformed  by family-based treatments in several trials
• CBT at group level or at individual level are equally effective
• MI as a standalone approach has given mixed results
• Integrated models uniformly performed well