Review of Prevention of Cannabis Use 

i) Cannabis is the most commonly reported illicit drug of choice among young people^1,2. There is, however, little evidence with regard to school-based programmes, which specifically address prevention of cannabis use. According to Milford et al. (2000)³, there is tertiary level evidence to suggest that generic drug education can prevent the use of cannabis. However, it must be noted that school-based drug prevention programmes can be effective in prevention of all types of drug use among both non-users and users. These effects are small and short-term⁴. Long-term  (6 years) prevention effects on cannabis use have been found for Life Skills Training programmes, but only among those who received the programme with high fidelity of implementation^5,6.  

ii) Summarising the available evidence, Milford et al. (2000)³ highlighted that effective cannabis prevention programmes consisted of interactive interventions aiming to increase knowledge on the effects of all types of drugs, inter- and intra-personal skills training, and promoting unfavourable attitudes about drug use. These programmes need to be small in scale and be delivered before students start to use cannabis³. There is evidence that community prevention approaches prevent the onset of regular cannabis use⁷. Research findings have indicated that cannabis prevention should address the social context of the young users, which often discourages conventional values such as educational achievement and promotes an early transition to adulthood⁸. A recent briefing paper on cannabis prevention⁹ has cited guidance on drugs for schools published by the Department for Education and Skills¹⁰. This document has emphasised that practitioners should teach about all drugs. However, there may be situations where they may need to specifically address cannabis (e.g. when there has been a cannabis-related incident). They also need to highlight that cannabis is still illegal. However, as a result of government campaigns coinciding with reclassification, there does not seem to be great misunderstanding about the legal status of cannabis[1]. After the campaign there was an increase in the percentage of individuals believing cannabis to be illegal (88 à 93%); believing smoking cannabis could be harmful (74 à 81%); awareness in the law change (38 à 61%); and a decrease in the number reporting that they would take cannabis if offered (17 à12%). 

iii) Interventions which are based on cognitive behavioural interventions (CB) and motivational interviewing (MI) have been used to treat cannabis use disorder^9,10. A review of several randomised controlled trials has revealed that these interventions were significantly effective in treating cannabis use compared to control but the relative clinical effectiveness of these interventions was very similar⁹. Results from recent randomised controlled trails in the US, which examined the efficacy of five types of cannabis treatment for young people, have also shown that all types of treatment tested (brief & standard CB and MI, family therapies, and community-based intervention) have demonstrated a similar positive impact on cannabis outcomes¹¹. However, it must be noted that there was no control group in this study and the majority of the sample was male offenders with self-reported mental health and/or behavioural problems (e.g. alcohol use, conduct disorders). A randomised trial in the UK has shown significant treatment effects of a brief MI on drug use including cannabis use among non-treatment seeking young people¹². The marked post-intervention effects diminished at the 12 months follow-up but the level of reported cannabis use was significantly lower than baseline¹³. This indicates that more research is needed to determine possible usefulness of booster sessions.  

Reference List

1.Chivite-Matthews, N., Richardson, A., O'Shea, J., Becker, J., Owen, N., Roe, S., and Condon, J. Drug misuse declared: Findings from the 2003/04 British Crime Survey. England and Wales.  London, Home Office. Home Office Statistical Bulletin. 2005.

2.National Centre for Social Research/National Foundation for Educational Research. Smoking, drinking and drug use among young people in England in 2004: Headline figures.  9-3-2005. London, Department of Health. 2005.

3.Milford R, Lenton S, Hancock L A critical review and analysis: Cannabis education in schools. New South Wales, Australia. New South Wales Department of Education and Training, Student Service and Equity Programs. 2000.

4.White D, Pitts M (1998) Educating young people about drugs: A systematic review. Addiction 93:1475-1487

5.Coggans N, Cheyne B, McKellar S The Life Skills Training Drug Education Programme: a review of research.  Scotland, University of Strathclyde. Scottish Executive Effective Interventions Unit, Scottish Executive Drug Misuse Research Programme. 2003.

6.Gorman DM (2002) The "science" of drug and alcohol prevention: The case of the randomized trial of the Life Skills Training programme. International Journal of Drug Policy 13:21-26

7.National Drug Research Institute and the Centre for Adolescent Health in Australia Monograph: The prevention of substance use, risk and harm in Australia: A review of the evidence. Common wealth of Australia 2004

8.Lynsky M, Hall W (2000) The effects of adolescent cannabis use on educational attainment: A review. Addiction 95:1621-1630

9.Drugscope. Cannabis: A briefing paper for drug education practitioners. London, Drugscope. 2005.

10.   Department for Education and Skills. Drugs: Guidance for schools. London, DfES. 2004.

11.   McRae AM, Budney AJ, Brady KT (2003) Treatment of marijuana dependence: A review of the literature. Journal of Substance Abuse Treatment 24:369-376

12.   Copeland J, Swift W, Roffman R, Stephens R (2001) A randomized controlled trail of brief cognitive-behavioral interventions for cannabis use disorder Journal of Substance Abuse Treatment 21:55-64

13.   Dennis M, Godley SH, Diamond G, Tims FM, Babor T, Donaldson J, Liddle H, Titus JC, Kaminer Y, Webb C, Hamilton N, Funk R (2004) The Cannabis Youth Treatment (CYT) study: Main findings from two randomized trials. Journal of Substance Abuse Treatment 27:197-213

14.   McCambridge J, Strang J (2004) The efficacy of single-session Motivational Interviewing in reducing drug consumption and perceptions of drug-related risk and harm among young people: Results from a multi-site cluster randomized trial. Addiction 99:39-52

15.   McCambridge J, Strang J (2005) Deterioration over times in effect of Motivational Interviewing in reducing drug consumption and related risk among young people. Addiction 100:470-479