What Are the Links between Cannabis And Schizophrenia?

It’s crazy how quick people are to class their opinion as fact, particularly in relation to cannabis and its alleged crazy-making properties. Facebook is the worst culprit in this regard, but often politicians, journalists and even doctors are just as bad. Like most anything to do with the plant, the awful truth about cannabis and schizophrenia is mired in conflicting evidence.

The general consensus amongst scientists is that people with schizophrenia are more likely to consume cannabis than people without the condition, which leads to the correlation v. causality debate. It’s a debate that’s tied to the demonisation of cannabis by officials and propagandists, beginning in the early twentieth century.

What Started the Debate?

Until the 1920s, there were up to 30 products available from western pharmacies without a prescription that contained cannabis, and American doctors wrote three million cannabis-related prescriptions a year to treat a variety of conditions. Back then, the general public were familiar with the terms cannabis and hemp, knew and understood their uses. To demonise cannabis, prohibitionists introduced the word marihuana to confuse people, and it worked.

When the Mexican Revolution began in 1910, millions of Mexicans flooded across the border bringing with them an herb they called mariguano, and in America, they and the plant were quickly shamed. “All Mexicans are crazy and this stuff is what makes them crazy,” one Texas legislator said, a sentiment that haunts cannabis to this day.

Beginning with Massachusetts in 1911 and through the 1920s, 27 U.S. states outlawed cannabis. A number of countries, mostly colonies such as South Africa, Canada, Sudan, and Australia also banned cannabis in the 1920s.In America, it was the 1937 Marihuana Tax Act that damned cannabis.

There are a few theories on events led to the Act but no question the campaign was led by Harry J. Anslinger, then chief of the Federal Bureau of Narcotics (FDN; predecessor of today’s DEA.) With the financial backing of interested parties that may have included the petrochemical and alcohol industry as well as William Randolph Hearst, they launched a tirade of propaganda that terrified nations.

The Threat of Insanity

Headlines like: “Marihuana: Assassin of Youth,” and the film, Reefer Madness (1936), cemented the idea in the minds of people that weed made you crazy. However, it was Anslinger’s testimony at the congressional hearing for the Act that did most damage. “Marihuana is an addictive drug which produces insanity, criminality and death,” he said, though he had no medical or scientific evidence to back up his claim. He did call on a number of “experts,” one of which was a pharmacologist named Dr. James Munch who had injected cannabis oil into the brains of 300 dogs; two died.

When asked if he chose dogs because their brains were similar to those of humans, he replied that he didn’t know, as he wasn’t a “dog psychologist.” When the bill passed, Anslinger made Munch the official marijuana expert of the FDN, a position he held till 1962. The congressional trial lasted less than two minutes and when the bill was passed, then American president, FDR, signed it into law.

After the bill was enacted, a number of 1940s court cases bolstered claims that marijuana use led to insanity when the defendants in five murder trials pleaded not guilty by reason of insanity due to marijuana use, and won. In one case, Munch testified for the defence saying that after two puffs on a joint he turned into a bat. “Killer Drug Turns Doctor to Bat!” the headlines said the next day.

By 1941, doctors had quit prescribing cannabis, and it had disappeared from medicine cabinets in the home. In 1942, cannabis was removed from the American Pharmacopeia. Yet, after 45 years and 1,800 studies, America’s National Institute on Drug Abuse (NIDA) has failed to prove that cannabis has any damaging effects on human health, but continues to release regular reports linking cannabis to everything from memory loss to psychosis.

In 1970, the Controlled Substances Act banned cannabis at a federal level in America, classing it as a Schedule 1 drug with no medicinal value. Yet, in 1998, the American government patented the findings of a study that showed cannabinoids act as neuro-protectants with the ability to limit the damage of stroke and trauma as well as protect against Alzheimer’s, Parkinson’s and HIV dementia.

From Insanity to Uncertainty

The first study to support the idea that using cannabis leads to increased risk for schizophrenia took place in 1969 in Sweden on 50,000 18-year-old army recruits. A 15-year follow-up recorded a six-fold increased risk for schizophrenia, which led a 27-year follow up that reported a threefold increase if the recruit had used cannabis more than 50 times in his life. Various other studies such as the Netherlands Mental Health Survey and Incidence Study found similar increased risks.

Further research came up with alternative explanations. One set of later studies identified similar brain pathways in cannabis users and schizophrenics while another found that schizophrenia patients may have endocannabinoid deficiencies independent of cannabis use. More recent studies conclude the genes that predispose a person to schizophrenia also lead to cannabis use, however that’s not the same saying cannabis use leads to schizophrenia.

Here’s the most damning evidence: cannabis use has increased ten-fold amongst teenaged populations since the 1960s but incidences of schizophrenia have remained consistent at 1 per cent over that time. If cannabis use led to schizophrenia in the way some research suggests, thousands of users could lose their minds any day now. Is that what they want us to think? Dr. Lester Grinspoon, associate professor of psychiatry at Harvard, and author of Cannabis Reconsidered (1971) is featured on the documentary, The Culture High, where he calls the whole debate, “ridiculous.”

Plus, I don’t know about you, but I find it hard to trust any studies when the data is epidemiological and known to be problematic. Studying the varying lifestyles of thousands of people and attempting to draw conclusive results is akin to herding cats, except worse because humans make flawed and unreliable subjects; translation: we lie a lot. Also bear in mind that the subjects of these studies are some of the most vulnerable people in society, the abused, marginalised and mentally ill.

Ultimately, there are so many studies out there on cannabis and mental disorders, it’s possible to select the relevant ones to prove or disprove any argument, leaving the whole question conveniently vague for anyone who might want to use the research to demonise the plant. Put simply, the links between cannabis and schizophrenia are tenuous at best, and a manipulation of facts at worst. While uncertainty prevails, the best course is to question everything, and be vigilant of opinions parading as fact. ‘Cause if the cannabis doesn’t make you crazy, my freaky friends, the conflicting evidence will.


“Big Bad Scary Weed,” Ch.1. “Brave New Weed, Adventures Into The Uncharted World of Cannabis,” Joe Dolce, HarperCollins, Oct. 2016.

#followtheplant #cannabisheals #sacredplant

Published by The Healthy Hashhead

The Healthy Hashhead is a writer, poet, cannabis educator and sports nutritionist, dedicated to spreading the message of the conscious consumption through unique content that speaks to regular users of cannabis.

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