A Link Between Marijuana, Schizophrenia Is Tenuous

NEW YORK: Samuel T. Wilkinson’s attempt to tie marijuana to mental illness (“Pot-Smoking and the Schizophrenia Connection,” WSJ op-ed, July 2) is reefer madness all over again.

The evidence indicating a causal relationship between marijuana consumption and mental disorders is “neither very new, nor by normal criteria, very compelling,” according to research published in the journal Addiction in 2010.

More tellingly, a 2009 study published in 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.

Mr. Wilkinson’s call for an honest debate about the health effects of marijuana is commendable. Yet such a dialogue is incomplete without an examination of its relative harms compared with others commonly used and accepted in our society, particularly alcohol.

Every objective study on marijuana has concluded that it is less toxic, it is less addictive and poses fewer and far less severe health problems than alcohol. Whereas there is no compelling evidence that marijuana use causes schizophrenia or psychosis, absolutely no doubt remains among members of the scientific community that alcohol use is a major contributor to mental illness. Also, unlike alcohol, marijuana use has never been linked to violent crimes and reckless behavior.

As long as alcohol is legal, anyone who is truly concerned about maintaining public health and preventing mental illness should support making marijuana a legal alternative for adults.

Mason Tvert

Marijuana Policy Project



Dr. Wilkinson suggests that the link between early pot smoking and schizophrenia should be recognized in the overall consideration regarding the legalization of pot. I agree. This link represents a good reason to proceed with the legalization process rather than to derail it.

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.

George W. Iliff

Port St. Lucie, Fla.


Marijuana is a drug that is extremely harmful to the human brain. Studies have shown that teens using marijuana before age 18 are two to four times more likely to develop psychosis as young adults compared with those who do not use marijuana. The teen brain is much more vulnerable to addiction. One in six children who try marijuana before age 18 will either abuse it or become addicted to it, compared with one in 25 adults. Research shows that THC, the key chemical in marijuana, if used during adolescence can change the way the brain develops. Specifically, the hippocampus is affected by marijuana, which is critical for learning and memory.

Because nerve cells in the human brain don’t finish developing until people reach their mid-20s it is pivotal to protect developing brains from the harmful effects of marijuana at a time when teens are incapable of making decisions that weigh pleasure, risk and consequence.

Carlos Alberto Hernandez

San Antonio, Texas


Dr. Wilkinson makes an extremely tenuous link between pot smoking and schizophrenia. Statistics cannot prove a causal relationship (100% of individuals who ate tomatoes in the 1860s have died). Schizophrenia is a disease that frequently presents in the late teens or early 20s, an age of drug experimentation, and it is quite possible that pot use unmasks the disease. But to say that otherwise functioning people are pushed over the cliff is unwarranted.

Jack Hutton, M.D.

Port Townsend, Wash.


Dr. Wilkinson gives readers the false impression that there is something unique about marijuana that somehow justifies marijuana prohibition. Yes, marijuana poses a risk to persons with a predisposition toward schizophrenia. So does alcohol, cocaine, amphetamines, etc. There is a strong correlation between schizophrenia and substance abuse. Addiction to nicotine (tobacco) is three times higher among schizophrenics than the general population. Correlation does not equal causation however, and schizophrenia rates have remained steady for decades, despite fluctuating drug use trends.

Robert Sharpe

Policy Analyst

Common Sense

for Drug Policy


Read full article @ Wall Street Journal