Many people sneer at the idea that addiction is a disease. "Surely so-and-so can just stop drinking" they say about alcoholics, unaware that an alcoholic can't control his craving for more drink -- just as a cancer or diabetes patient can't control the progression of his disease. Anyone who knows an alcoholic, or a hard core drug addict, will know that many of them desperately want to give up but are unable to.

When I was a student I thought cannabis was a harmless pastime, no worse than alcohol, and I was encouraged by the fact that it's not addictive. Many years later I ended up working for an addiction rehab clinic in Scotland where I found out that not only is cannabis addictive but the skunk version of the drug is known to send as many as 20% of users into a psychotic state.