More threads by David Baxter PhD

David Baxter PhD

Late Founder
Marijuana Abuse Contributes to Schizophrenia, Psychosis
Wednesday, February 21, 2007

Some believe marijuana to be relatively harmless, especially when compared to other illicit substances. But, according to a new study published in the journal of Current Psychiatry, mental health experts know better. Collected evidence adds weight to the idea that, in addition to its obviously detrimental physical side-effects, marijuana abuse/dependence may intensify the symptoms of psychosis in patients with mental illness and increase the chances that healthy subjects will eventually develop the same conditions. This theory first arose more than four decades ago when use of the drug was first becoming acceptable to mainstream America, but many clinicians assumed at the time that psychotic patients were simply more likely to use marijuana as a self-medicating sedative.

Today, the common caricature of marijuana users growing increasingly paranoid about imagined or exaggerated threats is supported by clinical research. As a result of cannabis-induced psychosis or pre-existing schizophrenia complicated by smoking pot, users may experience the type of episodes more often associated with higher-level hallucinogens. Examples include periods of severe psychological discomfort, anti-social behavior and withdrawal, and an increasing tendency to "lash out" at perceived enemies who may include innocent bystanders or family members.

Much like alcohol, the adverse effects of marijuana and its potential for abuse correspond closely to the age at which subjects first come into contact with the substance. The human brain is still forming throughout adolescence, and regular exposure to such intoxicants can actually alter the development of the body's neural pathways, leading to familiarity with, tolerance for, or addiction to the drug(s) in question. Teenagers are particularly susceptible to developing harmful and potentially long-lasting habits whose influence extends beyond physical addiction:

One 15-year study of 50,000 young people in Sweden, for example, found those who had tried marijuana by the time they were 18 were 2.4 times more likely to receive a diagnosis of schizophrenia.​
While some criticized this study as imprecise and overstated, newer, more specific research again indicates that adolescent pot smokers are more likely to develop schizophreniform disorders, particularly if their first usage occurs before the age of fifteen. Additional longitudinal studies display a clear association between marijuana and psychosis even after adjusting the data for pre-existing conditions, additional drug use and related factors. The chances of any teenager developing schizophrenia after puffing on a single joint are obviously remote, but all relevant research names regular, long-term abuse as a contributing factor, and young people with predispositions toward psychosis are particuarly vulnerable. Marijuana is in no way a harmless substance, and because the vast majority of teenagers will eventually come into contact with it in some form, they should be made aware of its psychotic implications:

Although marijuana use is not a "necessary" causal factor in psychotic illness, most users do not develop the disorder, and many persons with schizophrenia do not use marijuana, strong evidence indicates that it is one of many factors that can cause a psychotic illness.​
And this should be reason enough for teens to stay away.


One 15-year study of 50,000 young people in Sweden, for example, found those who had tried marijuana by the time they were 18 were 2.4 times more likely to receive a diagnosis of schizophrenia.

I found this study very interesting and wonder if there has ever been a study about other diagnoses besides schizophrenia. I have often wondered also whether the use/abuse of marijuana and other more serious drugs in adolescence can affect the brain (considering that it is still being developed) and ultimately can put a person at a higher risk for developing a mental illness?

David Baxter PhD

Late Founder
I can tell you that in my own clinical practice I have seen several cases where cannabis use triggered panic disorder or OCD symptoms. That's anecdotal evidence only, of course, but I have no doubt in at least some of those cases that the first episode was directly triggered by cannabis use. It's also clear to me that regular use can worsen symptoms of depression and generalized anxiety disorder.


Thank you David for your reply and for sharing what you have seen in your clinical experience. I have to say that I am quite interested in this :)


It's also clear to me that regular use can worsen symptoms of depression and generalized anxiety disorder.

Thank you Doctor Baxter for that informative article.

Personally I have absolutely seen regular use of "pot" make depression worse.

That frightens me because my ex husband was/is a big fan of cannabis. I don't smoke. I tried it once as a teen and hated it. My daughter started smiking ciggies and my ex husband told her he much rather she smoke pot then cigerretes. Needless to say I'm not happy with that one. They both are prone to SAD. He'd smoke to cheer up. Oh he'd be happy as heck, but later he was all the worse for it.

Thank you again. Interesting stuff.


Hi to everyone,

Just want to put my little bit in here as this subject is a very touchy one in my family. We often have debates about it but usually there is only one person out of step and that one is the 'user' in the family.

The rest of the family has seen first hand what it (and other drugs of course) can do. My son never had a problem with panic attacks or OCD or depression before he started using drugs. Now, even if he is not using anything else and 'only' smokes 'pot' it is very obvious to everyone as his personality changes. Thanks for letting me have a say. K9
Replying is not possible. This forum is only available as an archive.