By SAMUEL T. WILKINSON [Wall Street Journal] – Those not familiar with epidemiological causation may wonder how cannabis could “cause” schizophrenia if so many people who smoke marijuana or hashish don’t develop the disease. As an example, medical researchers have known for several decades that smoking causes lung cancer, yet over 80% of smokers do not develop lung cancer.

As research accumulates, the emerging picture is that marijuana precipitates schizophrenia or related psychotic disorders in people whose brains are inherently vulnerable to psychosis. All of us who do not regularly experience hallucinations or delusions reside on what may be called a “cliff of sanity.” Some of us, for reasons still unclear (thought possibly to be genetic), are closer to the edge of the cliff than others.

Marijuana may push everyone a few feet closer to that cliff. For those who were already close to the cliff, the drug pushes them over the edge into the chasm of insanity, hence precipitating the development of schizophrenia.

The association between schizophrenia and marijuana is not the only issue at play in the debate over marijuana legalization. If legalization is certain to decrease the power of drug lords in Mexico and other countries, then this is certainly a favorable outcome. However, if the trade-off is that more people suffer from schizophrenia—and thus more Americans are homeless and debilitated—then this must be recognized and discussed by the general public. This association between marijuana and serious and devastating psychotic disorders has been absent or under-recognized in the public debate.

Continued at The Wall Street Journal | More Chronicle & Notices.