Nearly twice the chance of psychosis. That's the conclusion of lengthy research carried out by the University of Maastricht into the relationship between the use of cannabis during puberty and psychosis in later years. The answer has been suspected for some time but has now been scientifically confirmed.

The Dutch research team led by psychiatrist Jim van Os writes in the British Medical Journal that:
"people who use cannabis at an early age have a dramatically increased risk of psychological problems later in life and continued use increases the chance of developing psychosis."
The conclusion is still valid even when factors like age, gender, socio-economic status, use of other drugs and other psychological problems are taken into account.

Which came first?
The conclusion is formulated with the usual scientific reserve, but the link between early cannabis use and psychosis is clear. A near is is clear. A near doubling of the number of cases is a result most researchers can only dream of.

The study confirms suspicions which have existed for years, among both scientists and social workers. One look at the streets of Amsterdam and even a layman can see that some cannabis smokers are seriously confused. The question is whether these are people with existing psychological problems who are in search of the calming effect of cannabis?

New users
The study carried out by Maastricht University began in 2001 and continued for ten years. Researchers worked with nearly 2,000 adolescents and young adults in Germany between the ages of 14 and 24.

Test subjects who said they had already used cannabis were excluded from the study as were people with existing psychological problems. The idea was to establish a link between "new" cannabis use and psychosis, with various external factors influencing the results.

Very unwise
Until now, reports of cannabis users suffering from psychosis were criticised on the grounds that psychiatric patients often turn to drugs as a form of "self-medication".

A spokesperson for the Dutch Trimbosch Institute for Mental Health and Addiction commented: "We see no reason to starting arguing against the legalisation of soft drugs in the Netherlands, but it is a fact that cannabis use at an early age is very, very unwise."

(imm)