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Psychotic disorders like schizophrenia usually strike young adults just as they are beginning life on their own. Children and teens who have used marijuana, however, may suffer these disorders three to 9 years earlier, as soon as the age of 12.

The Question is Whether Marijuana Causes Psychosis or Psychosis Encourages Marijuana Use

Matthew Large, a senior staff psychiatrist at Prince of Wales Hospital in Sydney, Australia, who headed the study conducted with other researchers at the University of New South Wales, told Reuter's Health, "We have to (tell) people who have marijuana in their pockets not to give it to younger people."

Publishing their findings in the 7 February 2011 online edition of the medical journal Archives of General Psychiatry, Dr. Large and his colleagues studied studies (that is, they did not work with any actual patients in this project) to see if the age of onset of psychotic disorders might be lower in children who had issues with substance abuse. Looking at 443 articles, and rejecting 360 they did not like, the Australian researchers concluded that the medical literature tells us that there is a statistical relationship between use of marijuana and age of onset of schizophrenia.

Correlation, however, is not the same as cause. The now well-publicized meta-analysis by Large and colleagues only tell us that it is reasonable to question whether marijuana use may cause acceleration of psychotic tendencies.

One way of explaining the findings of the Australian researchers is the simple fact that many of the studies  included in their analysis defined marijuana use in terms of "cannabis use disorder." This is a medical diagnosis.

This means the young marijuana users had already been identified before schizophrenia was diagnosed (and, presumably, medical care did nothing to stop the drug abuse). The fact that these children were already receiving psychiatric care increases the likelihood schizophrenia will be detected earlier.

That is, kids who smoke pot and go to psychiatrists are more likely to be diagnosed as schizophrenic than kids who neither smoke pot nor go to psychiatrist. And there are other explanations of the facts (besides what might have been in the 360 studies Large and colleagues left out). One of them is inflammation.

An Inflammation Theory of Schizophrenia

The Australian study doesn't prove that smoking marijuana as a child causes mental illness. It wasn't designed in a way to do that. It looked at correlation, not causation.

The National Comorbidity Study in Northern Ireland, for instance, found that childhood sexual abuse and childhood use of marijuana were highly correlated. No one supposes that childhood sexual abuse makes the same children use drugs, or that using drugs causes the child to sexually abused. Both conditions are outside a child's control.

Another explanation of the relationship between marijuana and schizophrenia is that schizophrenia is caused by inflammation of the brain, and since marijuana is a natural anti-inflammatory, children who are already have the brain inflammation that can cause schizophrenia self-medicate with pot.

Mr. Michael Rice, a nurse practitioner at the University of Nebraska Medical Center, theorizes that the inflammation theory may be a more useful explanation of the relationship of illicit drugs and psychosis. The inflammatory changes in brain tissue that lead to schizophrenia can be detected even at six and seven years of age. Very, very few children are introduced to marijuana at that tender age.

Children who have this pattern of brain inflammation, however, will be much more likely to use marijuana, and use it as often they can, if they are already on the pathway to psychosis.

Does this mean that marijuana use is somehow positive for troubled children? Dr. Kathryn Kotrla, associate dean of the Texas A & M School of Medicine in Round Rock, Texas, offers a path to a cliff analogy.

Developing Schizophrenia Likened to Falling Off a Cliff

Psychiatrists are not limited to dull summaries of inferential data. Like the rest of us, they can also develop their assertions in terms of word pictures and metaphor.

Dr. Kotrla of the medical school in Texas compares schizophrenia to falling off a cliff. Breaks with reality may manifest suddenly, but develop slowly. While the clinical diagnosis of schizophrenia may be like falling off a cliff, use of marijuana may cause the victim to go down the path much more quickly.

Mr. Rice and Dr. Kotrla both point out that schizophrenia is not a single disease, but rather 25 to 30 diseases with a similar origin. There are genetic factors, family factors, traumatic factors, and physiological factors. What pushes one person off the metaphorical cliff may not be what causes problems for another.

In general, at the first episode of schizophrenia:

  • Patients are three to ten times more likely to use some illegal drug.
  • Patients usually have engaged in a pattern of disrespect for authority and appear "maladjusted."
  • Patients whose drug of choice is marijuana often have better social skills, but their schizophrenic symptoms appear more acutely.
If marijuana "caused" schizophrenia, then why would other drugs also cause schizophrenia? And why would some studies find that children and teens who smoked pot were on some measurements better off than others who did not?

Kids with Schizophrenia Smoke Pot to Fit In

European studies find that teens with schizophrenia smoke pot and drink alcohol so that they can fit in with their peers socially. Even though the long-term effects of smoking pot make schizophrenic symptoms worse, the short-term social acceptance and relief from dysphoria, which is simply a state of feeling bad, are relieved by the drug. The even more commonly used alcohol has the same effect.

Certain other drugs, such as LSD and cocaine, on the other hand, can induce a psychotic break requiring immediate hospitalization. Alcohol and marijuana can cause acute problems, but are less likely to cause obvious psychiatric emergencies.

Is Dr. Large right? Should teens keep their marijuana in their pockets if they know their friends and peers have psychiatric problems?
Well, perhaps those teens should not have marijuana in their pockets in the first place, but there is a simple way to discern whether the person smoking marijuana needs to be referred to get mental health help. Marijuana does not typically cause the user to "trip out." When a user of marijuana sees things that are not there, hears, smells, feels, or fears things that are not there, there is a strong indication of an underlying disease process that might be leading to schizophrenia.

Teens who share their drugs do not make their friends schizophrenic, but they could be walking a friend that last step to the edge of the cliff.

  • Large M, Sharma S, Compton MT, Slade T, Nielssen O. Cannabis Use and Earlier Onset of Psychosis: A Systematic Meta-analysis. Arch Gen Psychiatry. 2011 Feb 7. [Epub ahead of print]