Cannabis

In his attack on Liberal Party anti-drugs policy, Gary Meyerhoff (Write On, GLW #656) contends that “despite claims by some mental health professionals that some pre-existing mental illnesses can be exacerbated or 'brought on’ by marijuana use, the evidence that supports this is extremely dubious”. I fear this is an instance of sloppy arguments serving a good cause.

While the level of psychiatric illness caused or exacerbated by cannabis is greatly exaggerated by many psychiatrists and politicians, not least John Howard in his recent COAG speech, this does not mean that the negative health effects of the drug are always “negligible”.

Gary mentions a study that shows the overall prevalence of schizophrenia has not increased in Australia over 30 years, despite a large increase in marijuana use. But this only proves that there is no simple causal link between the two. Recent Australian reviews of the issue (such as in the latest issue of the Australian & New Zealand Journal of Psychiatry) suggest the picture is much more complex than this.

Cannabis use is part of a dynamic set of risk factors that can contribute to various mental disorders. In the case of drug-induced psychosis or cannabis withdrawal syndrome, the connection is obvious. But in mood disorders and schizophrenia it is an additive in a complex web of causation. In particular, there is compelling evidence that heavy use of marijuana can affect the brain during key stages of adolescent development, when it is most vulnerable to environmental insults (whether chemical, psychological or social).

None of this is to suggest that anything other than decriminalisation and safe legal supply are sensible policies. But they need to be accompanied by honest discussion of both benefits and risks — something made more difficult by the polarised debate engendered by the current regime of criminal sanctions.

Dr Tad Tietze
Alexandria, NSW

Newshawk: http://www.napnt.org
Pubdate: Wed, 15 March 2006
Source: Green Left Weekly
Email: glw@greenleft.org.au
Website: http://www.greenleft.org.au