Does smoking marijuana increase the risk for schizophrenia?

Is pot use and psychosis related? Results from a meta-analysis published in the Archives of General Psychiatry:

...one finding that appears to be more consistent is that the use of cannabis is related to an earlier onset of psychotic disorders.

•The age of onset of the psychosis for cannabis users was 2.70 years younger than non-substance users.
•The age of onset of the psychosis of other (non-pot and non-alcohol) users was also 2 years younger than non-substance users.
•The age of onset of alcohol users was not different than the age of onset of non-users.