some time, studies and experts have noted the correlation between cannabis use and early onset of mental disorders such as schizophrenia. However, the findings of these studies were controversial because they did not consider other important factors. For example, not possible to distinguish the impact of cannabis from that of snuff, and that smoking marijuana is often mixed. Neither discussed the importance of sexual status or age differences and, therefore, had been criticized empirical value.

In an article published in the journal Archives of General Psychiatry (9-03-2011) with the title of Cannabis use and onset of psychosis Earlier, a research group, coordinated by staff of the University of New South Wales (Australia) has done the work to analyze and synthesize Overall, the results of 83 separate investigations on the subject, involving 22,000 participants. In this meta-analysis, as is known in scientific practice, the experts conclude that "the use of cannabis plays a causal role in the early development of psychosis in some patients."

Specifically, the study argues that marijuana use advances the onset of mental imbalances in 2.7 years versus non consumers. Unlike other studies, this one takes into account the weight of other substances, but is lower than that of cannabis. Among other things, ruled that consumption of alcohol has the same effects, nor that of snuff that the researchers did not cause exacerbation of psychosis.

From empirical studies, we can say that there is "sufficient evidence" to link marijuana use and early onset of psychotic illness. It does not indicate, however, that the habit of taking cannabis causes schizophrenia, but warns of risks that could have its use in people with a disposition to disease or what they call "sensibility", referring to the possible existence of a particular gene, which may explain why rates of schizophrenia are stable while increasing the consumption of marijuana.

Furthermore, Time (7 February, 2011) echoes other research that analyzed 190 cases of schizophrenia, noting that 120 of them had used marijuana. A subgroup of 44 patients, in addition, or had developed the first psychotic symptoms within the first month of use or when it had caused a significant worsening of symptoms. According

Archives of General Psychiatry, the results presented require rethinking some health policies, taking into account that according to national survey on drug use, 2009, in the U.S. more than 16 million people regularly use cannabis and that most of them begin to do so in the period adolescence.