Management of substance abuse

The health and social effects of nonmedical cannabis use

New WHO publication on cannabis


Chapter 8. Prevention and treatment

8.1 What do we know?

8.1.1 Prevention of cannabis use

There is emerging research on evidence-based prevention and increased knowledge on what is effective and what is necessary to implement and scale up preventive interventions. Most behavioural preventive interventions (environmental, universal, targeted and indicated approaches) have an impact on several problematic behaviours, including substance use (tobacco, alcohol, drugs and new psychoactive substances), and preventive interventions should cover the whole prevention chain from universal and selective to indicated prevention. This section of the document is limited to a short summary of those behavioural preventive interventions that are found to have a special beneficial or likely beneficial impact on cannabis use (in addition to other outcomes). Interventions aimed at reducing the harm associated with cannabis use by young people are included in section 8.1.2 on treatment. Widely adopted interventions without strong evidence of effectiveness, such as stand-alone media campaigns or information given alone to reduce drug use among young people (Ferri et al., 2013; Jepson et al, 2010), are not covered in this report.

8.1.1.1 Interventions targeting families

Family prevention strategies are thought to be “likely beneficial” (EMCDDA, 2013). A study of comprehensive family prevention that involved training for parents, children and the family collectively was found to be effective in reducing both lifetime cannabis use and past-year use in adolescents (Gates et al., 2006).

Furthermore, a Cochrane review of substance-use prevention found that family-based prevention programmes were more effective than youth-only programmes (Foxcroft & Tsertsvadze., 2011).There are additional encouraging results with regard to the long-term effects of family-based intervention on youth substance use (Foxcroft et al., 2014). Seven of eight family-based programmes examined in randomized controlled trials (six universal, two selective) showed positive effects during a period of at least two years (EMCDDA, 2015).

Some programmes provide adolescents or parents with services specific to their particular needs (Medina-Mora, 2005) and simultaneously address varying levels of risk (universal, selective and indicated) for both individual and family problems. A number of programmes of this kind have been tailored and tested, and those that have been evaluated have been found to have good results (Sanders, 1999). It may be less stigmatizing to reach these adolescents and families within universal-level prevention activities that target the whole population rather than in settings with more individually tailored intervention approaches (such as “programmes for families in need”).

8.1.1.2 Interventions in school settings

Life skills programmes that combine both a social competence curriculum and social influence approaches have been shown to reduce cannabis use at 12-month follow-up and beyond, as compared to controls (Faggiano et al., 2005). This kind of school-based intervention includes social skills lessons and interpersonal rehearsals, activities to boost self-esteem, refusal skills, skills in recognizing high-risk situations, and normative educational methods. School-based social influence interventions alone have been found to be effective in reducing cannabis use in one randomized clinical trial (Faggiano et al., 2010).

Another review of school-based studies has found that interactive drug curricula are more effective than non-interactive, lecture-based drug curricula. Over 200 such studies found a delay in onset of substance use and a reduction in youth cannabis use (Tobler et al., 2000). Peer-led interventions using peer educators in school settings have also been shown to be effective in reducing all substance use in a systematic review (McGrath et al., 2006). However, this effect was reduced by the one- and two-year follow-up points.

A Cochrane review in 2014 concluded that programmes based on a combination of social competence and social influence approaches seemed to have better results than other types of approaches, with effective results in preventing cannabis use at longer follow-up, and in preventing any drug use. Knowledge-based interventions showed no differences in outcomes, apart from knowledge, which was improved among participants involved in the programmes (Fabbiano et al., 2014)

Effective classroom management is shown to create a positive school environment that can be a proactive way to prevent several problems – including early onset of cannabis use – while creating a positive learning environment.

8.1.1.3 Interventions targeting vulnerable youth

Interactive, social programmes targeting vulnerable young people have been found to be effective in reducing past-month cannabis use. Programmes that provide life skills development, team-building content, interpersonal communication skills, and introspective learning involving self-reflection were found to be effective in reducing cannabis use in high-risk youth (Springer et al., 2004).

Other comprehensive approaches that combine the involvement of community, school and family have been found to be effective in a systematic review (Jones et al., 2006). This combined effort reduced use, delayed use and prevented use among high-risk adolescents when compared to community-only or school-only programmes (Jones et al., 2006).

8.1.2 Treatment of disorders due to cannabis use

8.1.2.1 Natural history of cannabis-use disorders

For many young people cannabis use is time-limited; it is most common in persons in their early twenties and ceases in their late twenties (Hall & Degenhardt, 2015). The long-term frequent cannabis users who have tried and failed to stop are those most likely to have cannabis-use disorders and to seek help from treatment services. Many persons who meet the criteria for dependence cease their cannabis use without treatment and they no longer meet the criteria for dependence when followed up a few years later. In Australia, the Victorian Adolescent Cohort Study, which tracked individuals dependent on cannabis for four years, found that more than half of those that initially met dependence criteria no longer did so after four years (Coffey et al., 2003). In a German study, over 80% of individuals who met criteria for dependence at an initial assessment were “in remission” at 10 years follow-up (Perkonigg et al., 2008).

8.1.2.2 Therapies for cannabis-use disorders

Brief psychological interventions based on motivational interviewing techniques have been shown to increase rates of cannabis cessation at 3 months (RR 3.33 [95% CI 1.99 to 5.56]) and at 8-12 months (RR 2.41 [95% CI 1.01 to 5.73]) (NCCMH, 2008). While this evidence has been used to promote very brief (as short as 5 minutes) opportunistic interventions in primary care settings, the trials identified in this review used trained psychologists to deliver interventions lasting 30-60 minutes.

While effective for harmful cannabis use, single-session interventions are of limited value in the treatment of cannabis dependence. A recent review by WHO found evidence from clinical trials to support the use of several approaches for the treatment of cannabis dependence, including combinations of measures to increase motivation (with motivational enhanced therapy [MET], cognitive-behavioural therapy [CBT] and contingency management [CM] providing specific rewards), together with family therapy interventions in adolescents (WHO, 2015).

CBT, MET and a combination of CBT, MET and psychosocial problem-solving therapy (PPS) were more effective than a waiting list control. CBT and MET produced a 50% reduction in continuous measures of cannabis use and were equally efficacious in head-to-head trials. For adolescents with cannabis dependence, family interventions were more effective than individual counselling in producing abstinence, and family and social interventions were more effective than psychoeducation alone.

An EMCDDA systematic review found similar results (EMCDDA, 2015). CBT and multidimensional family therapy, a type of family therapy, were found to reduce cannabis use moderately in adolescent users. MET/CBT combined with CM has also been shown to improve abstinence rates in this group. In contrast to the WHO review, MET alone produced results similar in effect to psychoeducation. Similarly, in the EMCDDA review of treatments for adult users, CBT and motivational interviewing (MI) in combination were found to be helpful, with MI alone producing a small effect (EMCDDA, 2015). In a review of trials which included patients with different substance-use disorders, keeping in mind that cannabis is the most commonly cited drug for treatment entry, family-based interventions – specifically BSFT, MI and CBT – were found to induce small but significant reductions in use (EMCDDA, 2015).

No medications have been found to be effective for treating cannabis dependence. A Cochrane review published in 2014 (Marshall et al., 2014) found that antidepressants, bupropion, buspirone and atomoxetine were ineffective, and that evidence was lacking for other potential therapeutic medications such as THC, gabapentin and N-acetylcysteine.

8.1.2.3 Management of acute cannabis intoxication and cannabis withdrawal

Various medications have been used to manage the acute effects of cannabis, such as anxiety, tachycardia, arrhythmias and psychotic symptoms. These medications include beta-blockers, antiarrhythmic agents, antagonists of CB-1 receptors and GABA-benzodiazepine receptors, antipsychotics and cannabidiol. Propranol, rimonabant, flecainidine, propafenone, flumazenil, olanzapine and haloperidol have all been used in the management of cannabis intoxication. There is a lack of data on the comparative effectiveness of different compounds in management of many of the acute presentations of cannabis intoxication; however, beta-blockers do reduce the tachycardia and hypertension associated with cannabis intoxication. It is likely that benzodiazepines will reduce anxiety in cannabis-induced panic disorders, although this has not been specifically tested (Crippa et al., 2012).

Arrhythmias from cannabis intoxication can be normalized by using antiarrythmic agents such as flecainide, propafenone and digoxin (Rubio et al., 1993; Kosior et al., 2001; Fisher et al., 2005). Flumazenil, an antagonist of the GABA-benzodiazepine receptor complex, has been effective in treating cannabis-induced comatose states that are fortunately very rare and typically occur when children accidentally ingest cannabis products (Crippa et al., 2012). Haloperidol and olanzapine have been found to be effective in reducing psychotic symptoms (Berk et al., 1999). Cannabidiol, a component of cannabis that does not produce psychoactive effects, has been shown to reduce anxious and psychotic symptoms induced by THC (Zuardi et al., 1982).

Different medications were evaluated in the management of cannabis withdrawal, including lithium (Winstock et al., 2009), lofexidine (Haney et al., 2008), nefazodone and bupropion (Carpenter et al., 2009) and, more recently, agonists of cannabinoid receptors such as dronabinol and nabiximols with encouraging results (Allsop et al., 2014; Allsop et al., 2015). However, the effectiveness of these medications in the management of cannabis withdrawal is not yet well established.

8.1.2.4 Relapse prevention

As with other substance-use disorders, relapse after cessation of cannabis use is common. To reduce the chances of relapsing to cannabis use and dependence, attention to the risk and protective factors associated with drug use may be useful. Risk factors for adolescents include conflict in the family and friends who use cannabis. Protective factors in adolescence include a positive relationship with parents, which provides structure and boundaries, a positive school environment, and engagement in activities that provide meaning (WHO, 2001). Protective factors in adulthood include employment, housing and social support. Risk factors include untreated mental health conditions.

8.1.3 Areas that require more research

·      The adverse health and social consequences of cannabis use reported by cannabis users who seek treatment for dependence are less severe than those reported by alcohol- and opioid-dependent persons (Hall & Pacula, 2010; Degenhardt, 2012). However, rates of recovery from cannabis dependence among those seeking treatment are similar to those for alcohol dependence (Florez-Salamanca et al., 2013). Clinical trials of cognitive behaviour therapy for cannabis dependence show that only a minority remain abstinent 6-12 months after treatment. Nonetheless, treatment substantially reduces the severity of cannabis-related problems and the frequency of cannabis use (Roffman, 2006; Danovitch, 2012).

·      Evidence on the effectiveness of telephone and Internet interventions is limited, although some reviews have reported reductions in cannabis use. This is an area for future research. These interventions may be of particular value in individuals who recognize that they have a problem with cannabis use but are not ready to enter an addiction treatment programme. This approach is also a cheaper option for countries with limited resources.

·       Few studies analyse the fidelity of the implementation of different psychological interventions so it is difficult to know with certainty that the interventions are the same across various countries or even various treatment centres within the same country.