On July 2, an article by Dr. Samuel T. Wilkinson was published in the Wall Street Journal positing that marijuana use can drastically increase one's predisposition towards schizophrenia and other mental illnesses. Dr. Wilkinson cites research stating that teenage and early 20s use of marijuana holds a causal link to later development of schizophrenia. However, this data is simply not a credible argument against making marijuana legal.
Within his own article, Dr. Wilkinson discusses the "cliff of sanity," a metaphorical line between sanity and mental illness, and he claims that those with a pre-existing tendency towards mental illness may be "pushed over" by marijuana use. However, if marijuana use before the age of 21 is riskier as a result of a developing brain, then legalization and regulation is the solution.
In response to the article, MPP's Mason Tvert said, "Legalization would involve carefully controlled outlets that would not sell pot to minors, as opposed to the current situation where illegal dealers will sell pot to anyone, including schoolchildren. The net effect would be less exposure to the drug by our young people at a time when they are most vulnerable."
In Mason's letter to the editor, he states that a 2009 study from the journal Schizophrenic Research found that "the prevalence of schizophrenia and psychoses has remained stable or declined during periods in which marijuana use increased significantly among the general populace."
A predisposition to mental illness is a preexisting condition that is not created by marijuana use. In fact, any chemical substance introduced into the body may very well exacerbate the issue, including alcohol. Marijuana does not cause mental illness for users, either occasional or frequent, and making marijuana legal poses the best chance for a safer marijuana market that more effectively limits access to people aged 21 and over.