Cannabis use and acceptance have increased among adolescents worldwide . Currently, cannabis is the most widely used illicit drug in most English-speaking countries such as Canada, New Zealand, Australia, and the United States . Despite being an illicit drug in Canada, one in seven adults and one in four students reportedly use cannabis . There are reports of an even higher prevalence of cannabis use in students (one in three) . A recent survey of middle and high school students in Nova Scotia found cannabis to be more widely utilized than cigarettes, and while 16.2% of adolescents used cigarettes, 32.4% used cannabis in 2007 . Furthermore, in a study carried out in New Zealand it was shown that almost 70% of a 21-year-old cohort population used cannabis . Cannabis use is even more striking in certain demographic groups. For example, in one survey 92% of street youth report using cannabis ‘in the past year’ and 16% report ‘daily use’ . Adolescents appear to be at a double disadvantage as they are more vulnerable to using cannabis  and the effects of cannabis on cognitive measures are more pronounced in adolescence [9,10].
In 1991, Boyle and Offord  wrote, “Despite the many studies that have reported associations between maladjustment and substance use in adolescence, we know little about the relationship between adolescents substance abuse and specific types of psychiatric disorders.” Other articles have made light of cannabis use, one calling it “safer than aspirin” . However, with such a high prevalence of adolescents
using cannabis it is imperative to firmly conclude whether the result of this action causes psychosis. At this point in time there are strikingly contradictory views regarding the possible neurobiological role of cannabis in triggering long-term psychosis, with some viewing the likelihood of long-term brain effects as unlikely  and others arguing that a lasting effect is likely . This article will review the
relationship of cannabis and psychosis as well as discuss the policy implications of these findings.