Myth: Marijuana use can lead to an increased risk of schizophrenia later in life.

The Truth: This is a total media scare story.  Different sources of this myth have different numbers.  Some say you are 4.5 times more likely to become schizophrenic if you smoke pot.  This “study” from the UK claims “Smoking just one cannabis joint raises danger of mental illness by 40%”.  Pretty scary isn’t it?  Fortunately these studies are total bullshit.

There have been many studies promoting the link between cannabis use and the onset of schizophrenia.  It is not the quantity of scientific studies that matters though, it is the quality.  As stated in some of my other marijuana myth posts there are three criteria that need to be satisfied in order to prove causality, these are: Association, Temporal Antecedence and Isolation.  Association means the cause and effect must occur together, temporal antecedence means the effect must follow the cause and isolation means all other causes must be ruled out.  The first two can be shown for pretty much anything.

For example if I performed a raindance and it rained later in the day I have satisfied association and temporal antecedence but not isolation.  Therefore I cannot scientifically prove that my raindance worked.  If raindances were a controversial topic the media would  then publish the “study” and the headline would read “Recent Study Suggests that Raindance Leads to precipitation”.  Sounds ridiculous right?  Well that is exactly what has been happening with the hundreds of “studies” on cannabis and schizophrenia.

Isolation has not been proven in the marijuana-schizophrenia link.  In fact evidence to the contrary is indisputable.  Marijuana use has grown significantly in the last 30 years.  If schizophrenia was caused by marijuana use then there should be an observable rise in schizophrenia rates as well.  No such link has been established.  This study from Australia demonstrates these findings (pdf).  Before marijuana became popular less than 1% of the population was diagnosed with schizophrenia, and now that marijuana use in widespread the rate of schizophrenia diagnosis is still less than 1%.

The Report of the Senate Special Commitee on Illegal Drugs from Canada in 2002 concluded the following,

No mental pathology directly related to the overuse of cannabis has been reported, which distinguishes this substance from psychostimulants such as MDNA, cocaine or alcohol, heavy and repeated use of which can give rise to characteristic psychotic syndromes. Similarly, cannabis does not seem to precipitate the onset of pre-existing mental dysfunctions (schizophrenia, bipolar depression, etc.).

Those suffering from schizophrenia are known to use drugs.  In a recent study, 60% of people with schizophrenia were found to use psychotropic drugs and 37% would be diagnosable with a substance use disorder.  It is assumed that people with schizophrenia use drugs to overcome self-esteem issues and negative feelings due to antipsychotic medication and the condition itself.  There are studies that show that cannabis can actually be used to treat the symptoms of schizophrenia (link1, link2).  The scientifically accepted factors that contribute to the onset of schizophrenia include genetics and social situations such as childhood abuse, poverty, and racial discrimination.  Social outsiders generally cling to drug use as a means to self-medicate depression or just add a little enjoyment to their lives.

Three-quarters of persons with schizophrenia develop the disease between 16 and 25 years of age.  The studies that suggest that marijuana causes schizophrenia claim that pot use during adolescence will cause schizophrenia around the age 26.  That is the age that it will occur anyway.  What does marijuana use have to do with it?  Nothing.  Persons who are predisposed to schizophrenia are awkward teenagers and much more likely to use cannabis and other drugs than their peers.  It actually looks like schizophrenia causes some marijuana use!

Despite lack of evidence the media promotes these studies as true.  Headlines like this, “UK researchers to claim as that pot is causing 14% of schizophrenia cases in the UK” are scary.  These media scare stories are unfounded and designed to create widespread fear around marijuana use, also known as propaganda.  The UK is currently in the middle of a psychological war on cannabis.  Check out some of these recent claims taken from a pot-schizophrenia news story,

Professor Robin Murray, of the Institute of Psychiatry in London, warned yesterday that the risks were likely to be heightened by the increasing use of powerful skunk cannabis.


Cannabis has been implicated in a string of vicious killings, including the recent stabbing of fashion designer Lucy Braham.

These claims are absurd this is pure propaganda.  Unfortunately the majority of people know very little about cannabis and accept these claims as true.