Is There A Connection Between Schizophrenia and Marijuana?

For years, in professional and public circles, debate has been ongoing regarding the relationship between schizophrenia and marijuana. Given the widespread legalization of marijuana in the United States and the increased acceptance of the drug as a result, the question of whether weed can cause schizophrenia has again come to the forefront.

In addition, this issue is garnering attention due to the high number of teenagers who use weed. According to the Monitoring the Future Study of 2018, almost 40 percent of 12th graders smoke marijuana. In fact, the survey found that teens are more likely to smoke weed than cigarettes. Furthermore, teens and young adults are also eating marijuana edibles, which are easier to get than ever before due to legalization.

Smoking Weed with Schizophrenia 

The question, “Can weed cause schizophrenia?” is a nuanced one. However, the statistics are clear on another correlation between schizophrenia and marijuana: Individuals with a stronger genetic predisposition to schizophrenia are more likely to start using marijuana, use it more regularly, and consume more of it over their lifetime.

Published in the journal Nature Neuroscience, a recent study used genetic data from the DNA ancestry database 23andMe. Researchers found a significant genetic correlation that indicates a higher probability of cannabis use by people with schizophrenia or emerging symptoms of schizophrenia.

According to another study conducted in the Netherlands, pot-smoking subjects with schizophrenia are more sensitive than healthy individuals to both the positive and negative effects of the drug. Although smoking weed made the subjects with schizophrenia feel better temporarily, it markedly worsened their psychotic symptomology.

Can Weed Cause Schizophrenia? 

The high likelihood of smoking weed with schizophrenia is well documented. But does the correlation go the other way: Can marijuana use trigger schizophrenia symptoms in an apparently healthy teenager?

According to researchers like Dr. Ran Barzilay, a child and adolescent psychiatrist at Tel Aviv University’s Sackler School of Medicine, the answer is yes—if the adolescent is already at risk for the disorder.

“Our research demonstrates that cannabis has a differential risk on susceptible versus non-susceptible individuals. In other words, young people with a genetic susceptibility to schizophrenia—those who have psychiatric disorders in their families—should bear in mind that they’re playing with fire if they smoke pot during adolescence.”

—Dr. Ron Barzilay

Research on the Connection Between Schizophrenia and Marijuana 

A 2018 study published in the Journal of Molecular Psychiatry adds to the substantial evidence regarding the association between marijuana and an increased risk of schizophrenia. This study clearly found that the relationship is causal and suggested that this evidence should inform policies and public health messaging about weed use, especially in reference to its potential mental health consequences.

In fact, another study found that cannabis use doubles the risk of developing psychosis in vulnerable people. Moreover, there is a relationship between the onset of schizophrenia and the age when a person first starts smoking marijuana—the younger the smoker, the higher the risk.

Early Signs of Schizophrenia 

If a teen does not have a genetic susceptibility to the disorder, smoking marijuana is not likely to lead to the onset of schizophrenic symptomology. However, there is no test for such a genetic susceptibility, and schizophrenia does not necessarily run in families. Therefore, it’s difficult to know whether or not a teenager is susceptible.

However, parents can watch for warning signs. Most people with the disorder receive a schizophrenia diagnosis in adolescence or young adulthood. Furthermore, onset is usually earlier in men than in women. Early symptoms may include the following:

  • Depression
  • Withdrawing from relationships and social activities
  • Trouble expressing emotion appropriately
  • Insomnia or sleeping too much
  • Talking in strange or irrational ways
  • Forgetfulness and inability to concentrate
  • Acting suspicious or hostile
  • Decline in personal hygiene.

Education on Schizophrenia and Marijuana Is Essential 

As a result, these warning signs indicate that a teen or young adult should have a professional mental health assessment. Schizophrenia treatment is typically multi-faceted, involving therapy, medication, and supportive changes in lifestyle and habits.

To summarize, marijuana does not cause schizophrenia, but research strongly suggests that it can trigger symptoms when an individual is already predisposed to the disorder. Therefore, parents should protect their children by educating them thoroughly about the link between schizophrenia and marijuana and becoming educated themselves.

Sources:

Drug Alcohol Depend. 2017 Feb 1;171:117–121.

Nature Neuroscience. 2018;21:1161–1170. 

Br J Psychiatry. 2010 Jun;196(6):447–53.

Mol Psychiatry. 2018 May;23(5):1287–1292. 

Int J Soc Psychiatry. 2018 Nov;64(7):690­–704. 

Human Mol Genetics. 2017 July;26(13):2462–2471.