Cannabis and the Brain

Across Europe and America, there is a groundswell of debate concerning the legalization of cannibas for personal use. Indeed, Britain has, to all intents and purposes, practically decriminalized marijuana usage. As a neuro-scientist, I am concerned about this debate.

One common justification for legalization or decriminalization of cannabis centers around the idea that it does not involve a victim. But at least four reports in major medical journals (Ramstrom, 1998; Moskowitz, 1985; Chesher, 1995; and Ashton, 2001), show the contrary. In a study of pilots smoking only a single moderate joint, there was a difference between a placebo control group and those taking cannabis, up to 50 hours after taking the drug. Other costs to the community are accidents at work or at home, educational under-attainment, impaired work performance and health budget costs.

Another argument for relaxing our attitude to cannabis is that it is non-addictive. Of course, defining `addiction' is hard, but if one regards it as an inability to give up, then there is strong evidence that cannabis incites dependence. Recent papers report many users in the US, UK and New Zealand now seek treatment for dependence. Other papers show that 10% of users want to stop or cut down, but have difficulties doing so, whilst a paper in 1998 reported that 10-15% of users become dependants.

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