This page refers to the current evidence on the effectiveness of the available treatment options for cannabis users. Information on the methodology used and the definition of terms can be found on the methodology page.
Date of last update: 12.2016 Next update: 04.2017
Ecological family-based treatments (including multidimensional family therapy) delivered in community settings were found in a systematic review without meta-analysis (Hogue et al., 2014) to have significant effect in:
Digital interventions (internet- or computer-based interventions) were found in a systematic review with meta-analysis (Hoch et al., 2016, 4 studies, N=1 928) to be effective in:
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:
The same meta-analysis also found that:
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:
No interventions met the criteria for this category.
Pharmacotherapies with different medications (eg. preparations containing tetrahydro-cannabinol (THC) (2 studies), selective serotonin reuptake inhibitor (SSRI) antidepressants (2 studies), mixed action antidepressants (3 studies), anticonvulsants and mood stabilisers (3 studies), atypical antidepressant (2 studies), anxiolytic (1 study), norepinephrine reuptake inhibitor (1 study), glutamatergic modulator (1 study)) were assessed in a systematic review (Marshall et al., 2014) finding no conclusive results on:
However, the review found that preparations containing THC compared to placebo were more likely to have effect than placebo in
Evidence-based international guidelines (WHO, 2014) do not recommend pharmacotherapy for routine treatment of dependence to stimulants and cannabis in pregnant women
Below you can find definitions and further explanation for some of the terms used in this section of the Best practice portal. A more general glossary for the best practice portal is also available.
A type of prevention intervention which aims to they aim to modify inner qualities (personality traits such as self-esteem and self-efficacy, and motivational aspects such as the intention to use drugs).
Before-after (BA) study design
Blood alcohol level (BAL)
Interventions for which precise measures of the effects in favour of the type of intervention were found in systematic reviews of relevant studies. An intervention ranked as ‘beneficial’ is suitable for most patients/contexts. See the relevant module methodology page for further information.
Controlled before-after (CBA) study design. UCBA stands for Uncontrolled before-after study design.
Cognitive behavioral therapy is an individual based intervention occurring in three stages. Phase 1 is aimed at determining and prioritizing the patient’s problems and constructing the treatment contract. Phase 2 is aimed at increasing coping competence and reducing risky behaviors. Phase 3 focuses on relapse prevention. Each session is administered once per week over a period of 4-6 months with 60- to 90-minute sessions (Beck AT, Wright FW, Newman CF, Liese B. Cognitive Therapy of substance abuse. New York: Guilford Press, 1993).
Controlled clinical trials (CCT)
A cohort study is a type of observational study that follows a group of people (i.e. a cohort) over time. In a prospective cohort study, the cohort is formed and then followed over time. In a retrospective cohort study, data is gathered for a cohort that was formed sometime in the past.
The Confidence Interval (CI) is a measure of the precision (or uncertainty) of study results. It is the interval that most likely includes the true value of the parameter we are calculating, where 'most likely' is taken by common usage to be a 95% probability. Thus the current expression of '95 % CI'. A wide CI indicates less precise estimates of effect and vice versa.
Current population survey (CPS)
A cross-sectional study is a study employing a single point of data collection for each participant or system being studied.They are usually conducted to estimate the prevalence of the outcome of interest for a given population at a given point in time.
Interventions that gave negative results if compared with a standard intervention or no intervention, for example. See the relevant module methodology page for further information.
Additional information for prevention
For ethical reasons this category in prevention should be considered as interventions with negative and undesired (iatrogenic) effect.
Individual psychotherapy is a standard individual treatment based on counseling and motivational interviewing and focused on substance use triggers and strategies for relapse prevention. It includes elements of cognitive-behavioral therapy (CBT).
Interquartile range (IQR) - also called the midspread or middle fifty - is a measure of statistical dispersion. It is a trimmed estimator, defined as the 25% trimmed mid-range, and is the most significant basic robust measure of scale.
Intermittent time series design (ITS)
Knowledge-focused prevention intervention
A type of prevention intervention which aims to to enhance knowledge of drugs, and drug effects, and consequences.
Interventions that were shown to have limited measures of effect, that are likely to be effective but for which evidence is limited. An intervention ranked as ‘likely to be beneficial’ is suitable for most contexts/patients, with some discretion. See the relevant module methodology page for further information.
The Number Needed to Treat (NNT)indicates the number of patients that needs to be treated to obtain one respondent patient. Numerically the NNT is the reciprocal of the difference between the proportion of events in the experimental and the comparison group (absolute risk reduction). Taking into consideration that the ideal NNT would be 1 (the unreal situation in which every single patient succeeded) it is easily understood that a NNT value close to 3 or 4 would be very good.
The Adjusted Odds Ratio is a way of comparing whether the probability of a certain event is the same between two groups, yet they are calculated adjusting for or controlling for other possible contributions from other variables (tipically demographic variables) in the model. An AOR equal to 1 implies that the the event is equally probable in both groups. An AOR greater than 1 implies that the event is more likely in the first group. An AOR less than 1 implies that the event is less likely in the first group.
The Odds Ratio is a way of comparing whether the probability of a certain event is the same between two groups. Like the Relative Risk, an OR equal to 1 implies that the the event is equally probable in both groups. A OR greater than 1 implies that the event is more likely in the first group. A OR less than 1 implies that the event is less likely in the first group. In medical research, the odds ratio is commonly used for case-control studies, as odds, but not probabilities, are usually estimated. Relative risk is used in randomized controlled trials and cohort studies.
A p-value is a measure of how much evidence we have against the null hypothesis. The null hypothesis represents the hypothesis of no change or no effect. The smaller the p-value, the more evidence we have against the null hypothesis thus it is more likely that our sample result is true. Traditionally, researchers will reject a null hypothesis if the p-value is less than 0.05.
Responsible beverage service (RBS)
Randomised controlled trial (RCT)
The Relative Risk (RR) is used to compare the risk in the two different groups of people, i.e. treated and control groups to see if belonging to one group or another increases or decreases the risk of developing certain outcomes. This measure of effect will tell us the number of times an outcome is more likely (RR > 1) or less likely (RR < 1) to happen in the treatment group compared with the control group.
Interventions that obtained measures of effects in favour of the intervention, but that showed some limitations or unintended effects that need to be assessed before providing them. See the relevant module methodology page for further information.
Interventions for which there are not enough studies or where available studies are of low quality (with few patients or with uncertain methodological rigour), making it difficult to assess if they are effective or not. Interventions for which more research should be undertaken are also grouped in this category.
Additional information for prevention
For prevention interventions, this is also known as 'zero effect'.
A type of prevention intervention which aims to enhance students’ abilities in generic skills, refusal skills and safety skills.
The Standardised Mean Difference (SMD) is the difference in means divided by a standard deviation. Note that it is not the standard error of the difference in means (a common confusion). The standardized mean difference has the important property that its value does not depend on the measurement scale. It may be useful if there are several trials assessing the same outcome, but using different scales.
The z-score (aka, a standard score) indicates how many standard deviations an element is from the mean of the population.
The Diagnostic and statistical manual, 5th edition, describes cannabis use disorder as a condition characterized by the harmful consequences of repeated cannabis use, a pattern of compulsive use, and (sometimes) physiological dependence (i.e., tolerance and/or symptoms of withdrawal). This disorder is usually diagnosed when cannabis use becomes persistent and causes significant academic, occupational or social impairment.
In most countries, cannabis use increased during the 1990s and early 2000s, and this has resulted today in a less varied European picture. It is the most-used illicit drug in Europe, although important differences between countries still exist.
Cannabis use is largely concentrated among young people (aged 15–34 years), with the highest levels of last year use generally being reported among 15- to 24-year-olds. Cannabis use is generally higher among males than females, though marked differences between countries are observed.
Conservatively estimated, cannabis has been used at least once (lifetime prevalence) by around 74 million Europeans — over one in five of all 15- to 64-year-olds.
Considerable differences exist between countries, with national prevalence figures varying from more than 1 % to almost 40 %. Many countries report comparatively high prevalence levels of last year and last month use of cannabis. It is estimated that around 22 million Europeans have used cannabis in the last year, or on average 7 % of all 15- to 64-year-olds. National prevalence estimates of cannabis use vary widely between countries in all measures of prevalence, with countries at the upper end of the scale reporting values up to 10 times those of the lowest-prevalence countries.
Specific treatment programmes for cannabis users provide services tailored to the needs of this group and also reduce the risk of young people mixing with more problematic and older drug users.
Services targeting cannabis users that are available in Europe include: early intervention programmes, comprehensive family-based treatment, counselling centres implementing specific concepts for young cannabis users, prevention information, brief interventions for users, young offenders and their relatives, Internet-based cannabis cessation programmes, motivational enhancement and cognitive behavioural therapy, psychosocial problem solving and motivational interviewing.
Treatments may not be effective in achieving all the desired outcomes, these outcomes are prioritised.
* studies such as National Treatment Outcome Research Study – NTORS, Australian Treatment Outcome Study – ATOS
Periodic cannabis use and intoxication can interfere with performance at school or at work and may be physically hazardous in some situations, for example driving. Individuals with cannabis dependence may use very potent cannabis and this may create problems with their performance at school and work, and lead to difficulties within their families. People with cannabis dependence can persist in its use in spite of related physical problems (e.g. chronic cough related to smoking) or psychological problems (such as a decrease in goal-oriented activities). (DSM-IV)
American Psychiatric Association (2000), Diagnostic and statistical manual of mental disorders, 4th edition, text revision, American Psychiatric Association, Washington, DC.
EMCDDA , Annual report: the state of the drugs problem in Europe, EMCDDA, Lisbon