Both the Mental Health Review Tribunal in NSW and the National Cannabis Prevention and Information Centre have said publicly that if cannabis was removed from the chemistry of young brains, the incidence of schizophrenia in this country would be dramatically reduced. Adolescents who start to use cannabis at any time are considered particularly vulnerable because the human brain does not complete its development until the early to mid 20s
http://www.abc.net.au/news/2011-05-24/high-risks-cannabis-and-psychosis/2729178