Does marijuana trigger schizophrenia?

Cannabis and schizophrenia: Trigger or treatment?

As marijuana is becoming more popular and usage is on the increase, the question is often asked, does it serve as a trigger or treatment to people living with schizophrenia?

After numerous tests, scientists have found a correlation between marijuana and schizophrenia. Through a study conducted by researchers at Columbia University Medical Centre, it's been found that the risk of schizophrenia is higher in individuals who have a family history, however, the use of marijuana is not a factor in the onset.[1]

Schizophrenia is a complex and chronic brain disorder that includes symptoms such as delusions, hallucinations, trouble with thinking and concentration patterns along with a serious lack of motivation.[2]

The study by the Department of Neurobiology at Columbia University Medical Centre has highlighted the following findings,[3]

  • People living with schizophrenia often use marijuana regularly, but, which came first? Using marijuana as a crutch for symptoms that pre-existed or were the symptoms induced by marijuana usage?
  • Another factor considered by the research team are the strains of marijuana and their varying strengths. The stronger the strain, the sooner the onset of schizophrenia in people that have a family history of the disorder. In cases where individuals had no family history, the findings were inconclusive.
  • To increase the levels of Tetrahydrocannabinol (THC), growers often add chemicals to make the high last longer. These chemicals are unknown to researchers, making the correlation unclear in some instances.
Effects of marijuana on a person not living with schizophrenia

The common factor between schizophrenia and marijuana consumption is a condition called ‘psychosis’. Not to be confused with the onset of psychotic behaviours, but rather causing a disruption in normal thought patterns. The symptoms of psychosis can be caused when THC levels are higher than 30%. However, these symptoms wear off as the effect of marijuana does.4

Effects of marijuana on a person living with schizophrenia

In contrast, the symptoms of psychosis for a person with schizophrenia increases with marijuana usage, which could result in severe outbursts, and potentially lead to psychotic behaviours.[1]

The burning question

The study concludes that marijuana does not directly lead to schizophrenia, however it increases the possibility of schizophrenia based on the following findings.4

  • If used by teenagers prior to their brain developing to its potential, they are at risk of being diagnosed with schizophrenia at an earlier stage than previous studies suggest.4
  • If used by individuals who use marijuana as self-treatment for schizophrenia, researchers made a crucial discovery in that the negative effects outweigh the positive effects.

If you know of anyone living with schizophrenia and using marijuana either for recreation or to self-medicate, encourage them to seek medical help.

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References

National Institute for Clinical Excellence. Psychosis and schizophrenia in adults: prevention and management. 2014. CG178.
APA Clinical Guidelines. American Psychiatric Association. Practice Guidelines for the treatment of patients with schizophrenia. 2004.
Hasan et al. World J Biol Psychiatry 2012; 13: 318─378.
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