Analysis indicated that for each year adolescent boys engaged in regular marijuana use, their projected level of subsequent subclinical psychotic symptoms increased by 21% and projected risk for subclinical paranoia or hallucinations increased by 133% and 92%, respectively.
Links
[1] http://www.healio.com/psychiatry/addiction/news/online/{aca14ce0-4b46-497a-b882-561f1c51060f}/marijuana-use-in-adolescence-may-increase-risk-for-psychotic-symptoms
[2] http://rethinkpot.org/tags/youth
[3] http://rethinkpot.org/tags/adolescent
[4] http://rethinkpot.org/tags/psychosis