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Reefer Madness?

A long-term Christchurch study shows some support for the idea that the use of cannabis by young people may encourage the development other problems of personal adjustment including crime and mental health problems, but that cannabis is not necessarily the sole cause.

A study of 1,000 Christchurch-born children has indicated that young people who began using cannabis before the age of 16 had increased rates of adjustment problems and difficulties at age 18. These difficulties included higher rates of juvenile offending, more frequent use of other substances and higher rates of mental health problems.

However, those using cannabis prior to the age of 16 also experienced other disadvantages that were present before they started to use cannabis. These include higher rates of exposure to family difficulties and problems, the early development of problem behaviours and the formation of affiliations with delinquent and substance using peers. This raises the possibility that linkages between cannabis use and adjustment problems arise because those using cannabis at an early age tend to come from high-risk backgrounds.

Statistical adjustment for events and circumstances prior to the onset of cannabis use suggest that, to a considerable extent, the higher rates of adjustment problems amongst those using cannabis, reflect social and personal circumstances that were present prior to the onset of cannabis use, rather than the direct effects of cannabis use on individual adjustment. Nonetheless even after such statistical corrections, young people who used cannabis prior to the age of 16 were at increased risks of later cannabis use, illicit drug use, juvenile offending, school dropout and unemployment.

Professor David Fergusson, Christchurch School of Medicine