its true that there isnt 100% conclusive proof linking cannabis to psychosis - but i think this article from

Dr Brian Boettcher (Consultant Psychiatrist Shelton Hospital, Shropshire??s Community & Mental Health Services NHS Trust) sums it up quite well....

"The drug induced psychosis seen when Cannabis is the main substance being abused is distinct phenomenologically from other psychosis.

It is unusual for such a psychosis to occur without other drugs being involved to some extent and so it is difficult to tease out the differences between the effects of Cannabis and other drugs.

However it is misleading and dangerous, to our youth in particular, to label Cannabis as ??soft?. In fact the serious adverse effects of Cannabis have been known for some time now and Hall and Solowij in the British Journal of Psychiatry sounded warnings in 1997 about such issues as dependence on Cannabis, adolescent developmental problems, permanent cognitive impairment as well as involvement in and the development of psychosis.[1]

There are suggestions that in a small number of cases Cannabis is capable of precipitating psychosis, going on to the chronic picture described below, in people who have had no family and personal history of psychiatric illness.There have been suggestions that such people may be the ones who have started Cannabis in their teens and caused disturbance to neural connectivity. However, it seems Cannabis can precipitate or exacerbate a schizophrenic tendency in a characteristic manner."

this authoritative and non-politicised opinion is widely accepted in the medical community in the UK......

not that im against legalisation by the way - drug induced psychosis only affects a very small proportion of users.....but it is a real condition. I personally 2 people who've suffered psychosis from smoking copious amounts of weed.....1 of whom has been sectioned twice.....MJ is a great drug but it aint 100% safe.....