Does Marijuana Cause Schizophrenia?


  • Schizophrenia affects 1% of the population and is mostly linked to family history
  • Studies suggest but do not provide strong evidence of a link between marijuana and schizophrenia
  • The rate of schizophrenia has not changed over the past few decades, although marijuana use has increased
  • Experts believe that marijuana use is only risky for individuals that are already prone to schizophrenia
  • However, research shows that schizophrenia patients can benefit from using marijuana – Schizophrenia is one of the most recognized mental disorders in today’s society.

While schizophrenia affects only 1% of the overall population, there seems to be a widespread fear among marijuana users of developing this condition. This fear stems from the common yet controversial belief that marijuana use increases the risk of schizophrenia.

What’s The Link?

Numerous studies published over the past few decades have suggested a link between marijuana use and schizophrenia, based on findings which show that a large proportion of schizophrenia sufferers also happen to be marijuana users.

For instance, a widely publicized review study published in 2007 concluded that trying cannabis just once could increase the risk of schizophrenia and related psychotic disorders by 40%.

On the other hand, these suggestions have never been confirmed by studies designed to evaluate a direct causal relationship. Instead, studies have only look back in time after schizophrenia was diagnosed to find that a disproportionate number of patients happened to be current or past marijuana users. As a result, the claim that marijuana use causes schizophrenia remains controversial and support among experts has gradually decreased as evidence of the contrary grows stronger.

Dr. Lester Grinspoon is an expert on schizophrenia.

Most experts who challenge the link between marijuana and schizophrenia cite population statistics which show that the rate of the disorder has remained steady over the past few decades, despite the fact that the rate of marijuana use has grown exponentially since the mid-20th century.

Dr. Lester Grinspoon is one of these experts, having specialized in the study of both schizophrenia and marijuana during his long career as a senior psychiatrist and Associate Professor at Harvard Medical School. According to Dr. Grinspoon, there has yet to be “even a blip in the incidence of schizophrenia in the US after millions of people started smoking marijuana in the 1960s.”

But while evidence of marijuana use causing schizophrenia is little to none, experts still believe that marijuana can cause earlier onset of the disease in individuals that are prone to developing the disorder. This was highlighted in the commentary of a panel of mental health experts published last year in the Journal of Clinical Psychiatry:

“The data suggest that cannabis use in early adolescence is associated with an earlier onset of schizophrenia in a vulnerable population…” – Dr. Alan I. Green

Dr. Green’s statement echoes the belief of most doctors today, which is that marijuana’s psychotic effects are only temporary for the vast majority of the population that are not at risk of developing schizophrenia.

Even still, the fact that psychosis is a common side-effect of THC is not enough to even say that marijuana has a detrimental effect on schizophrenics or schizophrenia-prone people. In fact, a number of studies seem to show that marijuana can be used as a treatment for the disorder, leading some experts to question whether cannabis use actually increases the risk of schizophrenia in vulnerable individuals or if higher rates of marijuana use are just a sign of patients’ attempts to self-medicate their symptoms.

Can Marijuana Treat Schizophrenia?

Oddly enough, studies show that marijuana can actually provide a variety of benefits to patients with schizophrenia.

For example, a study conducted in 2012 on 42 schizophrenia patients found that cannabidiol (CBD) was just as effective as the standard antipsychotic medication amisulpride in treating the psychotic symptoms of the disorder. Interestingly, the study also found that CBD was able to increase patients’ levels of an endocannabinoid called anandamide.

Anandamide naturally occurs in the human body and is just one part of the body’s natural cannabinoid system – the endocannabinoid system. Anandamide is also remarkably similar to THC in how it interacts with cannabinoid receptors by mostly binding to CB1 receptors. Interestingly, studies show that schizophrenics tend to have higher levels of anandamide than healthy individuals and patients with higher levels of anandamide seem to experience a lower intensity of symptoms related to the disorder.

Finally, a review study that evaluated the results of 8 prior studies found that schizophrenics who use marijuana experience improvements in overall cognitive performance spanning a variety of factors, such as memory, learning, and intellectual and language abilities.

What This Means For Your Health

Overall, there is diminishing support among the medical community of a link between marijuana use and schizophrenia. Instead, most experts believe that marijuana may interact with other risk factors to increase the possibility of earlier onset of the disorder in individuals that are already prone to developing schizophrenia. Unfortunately, scientists have yet to pinpoint the genetic make-up of schizophrenia-prone individuals, making it impossible to determine who is more likely to suffer from the psychotic effects of marijuana.

“Clinicians can tell patients and their families that marijuana use in the early teenage years seems to increase the risk of psychosis in some people. We currently cannot say which people are more vulnerable.” – Dr. Alan I. Green

Although the role of marijuana in schizophrenia appears to be both positive and negative, the fact remains that your chances of developing the disorder are mainly dictated by genetic factors, meaning that there is very little that anyone can do to avoid it. More importantly, it seems safe to say that using marijuana does not increase the risk of developing schizophrenia for the vast majority of the population.

However, marijuana use may lead to intense and long-lasting psychotic symptoms in the 1% of the population that will inevitably be diagnosed with schizophrenia. And while there is indeed evidence that points to marijuana as being a useful treatment for schizophrenia, if you happen to be someone who suffers from overwhelming psychotic symptoms after using marijuana, it is highly recommended that you consult with a doctor before deciding on whether it would be a good idea to continue with your marijuana use.

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