By Marvin Ross
Now that marijuana is legal in Canada and in many US states, understanding the role of this substance in the development of schizophrenia is even more crucial. Schizophrenia has long been thought to be associated with pot smoking but the causality has been in doubt.
In my book, Schizophrenia Medicine’s Mystery Society’s Shame published in 2008, I cited the research that was current at that time.
The classic study was that of a long term follow up of Swedish conscripts aged 18-20 in 1969-70. A total of 50,087 young people representing over 97% of that country’s 18-20 male population reported on their use of cannabis, other drugs and on several other social and psychological characteristics. The researchers then looked at hospital admissions for schizophrenia amongst this group. It was found that cannabis was associated with an increased risk of developing schizophrenia. The greater the use then the greater the risk. The researchers concluded that there was no question but that the link between the two was causal. Cannabis use caused schizophrenia and the link was not explained by the use of other psychoactive drugs or personality traits.
However, it has also been hypothesized that schizophrenia leads to a greater use of marijuana likely because people are trying to medicate themselves. A number of years after the above study was published, Scottish researchers looked at all the studies that had been done on the link between cannabis and schizophrenia between 1966 and the end of 2004. That study agreed with the original findings. Early use of cannabis does appear, it said, to increase the risk of psychosis and that cannabis is an independent risk factor for both psychosis and the development of psychotic symptoms. Again, it has been argued that prodromal symptoms of schizophrenia lead to an increased use of marijuana. Then, while the disease is developing, being stoned speeds up the developing deficits of the disease.
Malcom Gladwell in the New Yorker and New York Times reporter Alex Berenson recently wrote about the correlation between marijuana use and violent crime. Gladwell cited a National Institute of Medicine research report and Berneson produced a book on the topic called Tell Your Children: The Truth about Marijuana, Mental Health and Violence.
Marijuana researchers objected strenuously to the link of marijuana to crime and I tend to agree. But Gladwell also linked pot use to schizophrenia and that too set off the marijuana researchers. Ziva Cooper, one of the authors of the National Academy of Medicine report, objected to the association of marijuana with schizophrenia. She said that the National Academy did find a link between marijuana and schizophrenia but that they also found a link between using cannabis and improved cognitive outcomes for people with psychotic disorders.
Now that I can also believe but the researcher is mixing apples with oranges. Marijuana is comprised of THC which is the hallucinogenic and CBD which is not. It is the THC that can push people to psychosis and when smoking pot, you do not know how much of each is in the joint. And, of course, the potency of pot today is much greater than it was in my day.
According to a research update in Psychiatric Times “Cannabidiol (CBD), the second most active ingredient in marijuana, has been hypothesized to have antipsychotic effects—in contrast to tetrahydrocannabinol (THC), which may promote or worsen psychosis”. Recent research in the American Journal of Psychiatry found that “CBD has beneficial effects in patients with schizophrenia. As CBD’s effects do not appear to depend on dopamine receptor antagonism, this agent may represent a new class of treatment for the disorder”.
However, people should be aware that when you smoke a joint or nibble an edible, you have no idea how much THC or CBD is in the product.
And, as the brain continues to develop till about the age of 25, those under that age should be cautious particularly if they have a family history.