Cannabis and Schizophrenia Redux

We have already gone over this subject at length in a previous post. However, I am starting to change my mind on the subject after a lot of reading. It is looking more and more like heavy cannabis consumption during the teenage years is somehow implicated in the development of schizophrenia later on.

How this works is not known. Cannabis is probably not causing it directly, otherwise we should see epidemics of schizophrenia. More likely it is triggering it in a person who is already vulnerable. But the evidence has been flooding from, now from 30 different studies. And the younger the person is when they start and the more they use in the teen years, the greater the risk of schizophrenia later on. Some studies are even finding a dose-response relationship.

The fatal flaw in this theory has been that the rate of schizophrenia has not risen during since the start of the cannabis epidemic. I used cannabis for many years myself, and I known thousands of users, many of them long-term and heavy users. Other than making some young people lazy and somewhat paranoid, I haven’t seen a lot of ill effects from the drug.

I knew one guy who had schizophrenia who loved pot, but it made him a lot worse, so everyone tried to keep it away from him.

I’ve known only one marijuana user out of the many thousands of drug users that I have known who developed schizophrenia, but he was a heavy speed user for 10-20 years. He developed schizophrenia around age 37 after using methamphetamine heavily for 10-20 years. I am pretty sure that over a decade of heavy speed use caused his schizophrenia since heavy meth use causes massive damage to the brain.

I’ve never known any other cases, and I never saw any cases the whole time I was growing up. I hung out with heavy users, sold the drug myself for many years, and never saw any psychosis, not even a temporary case. However, the pot around nowadays is extremely strong and the age at first use has been dropping. I tried some recently and can testify that it is extremely strong indeed. I can handle it fine as I can easily handle just about any drug out there, but I can see how it could flip someone.

Quite a few of the local young people around here smoke pot. I’ve gotten to know quite a few of them and learned of their heavy marijuana use. They ranged in age from 16-23. A couple of them were dealers in their 20’s who were using large quantities of this very strong pot.

I knew about the pot-schizophrenia link and I kept looking for it in all of these individuals. I have yet to see a case of psychosis, much less schizophrenia, among these young people. I saw one person who got paranoid on pot, and I saw other cases of the “lazy pothead” syndrome, but in general, they were quite healthy mentally and led full and enriched lives. If cannabis is implicated in schizophrenia, it sure doesn’t cause it very often, as most even heavy users seem to avoid this drastic consequence.

Many kids are using this extremely strong pot at younger and younger ages, often daily for many years in adolescence. The pot we were using was much weaker, most of us did not use it every day, and most of us didn’t start using until around age 16 or so. Heavy use started around age 20 or so.

While cannabis in general does not appear to cause significant structural damage in adults, some very ominous findings are coming out about use in adolescence.

A recent study found that adults who started using cannabis before age 17 (16 or younger) had smaller brains overall, had less grey matter (fewer brain cells) yet more white matter (connections between neurons) (Earleywine 2005). Less neurons yet more connections isn’t exactly brain damage. Instead it’s just a brain that appears to have developed in a different way.

But this is the problem. The brain is still developing during adolescence. If cannabis impairs and changes normal brain development, this could be a bad thing. As it stands, no one should use cannabis before age 17 due to the risk of permanent brain changes of unknown significance. Delaying use until after age 16 apparently results in avoidance of these changes.

Even the most pot-critical researchers are claiming that cannabis is only causing 8-1

This interview was quite interesting. This psychiatrist posits that cannabis is causing schizophrenia, but only in people who use it, usually on a daily basis, for years starting in adolescence. The risk is greatest the younger you start. Delaying use until 19 or 20 results in dramatically lowered risk. The risk apparently drops to zero if one waits until age 21 to start using cannabis. In other words, I, at age 52, could smoke a ton of dope between now and the time I die and it won’t give me schizophrenia no matter how much I use.

At the very least, it’s certain that early and heavy cannabis use brings schizophrenia on sooner than it would have occurred ordinarily. However, that means years of life lost to psychosis that are gone forever. Many schizophrenics who use cannabis find that they have a worse course, as the cannabis triggers new psychotic episodes.

Yet schizophrenics seem to love the stuff, paradoxically. That’s probably because at first it seems to calm them down. Schizophrenia is a horrible illness, and sufferers will take just about anything to escape from the symptoms.

One theory that keeps coming is that is quite common in the early stages of schizophrenia (the prodromal phase) for users to turn to various drugs to relieve their distress. Schizophrenics often go years before their first diagnosis.

This article by Robin Murray, a notorious proponent of the cannabis-schizophrenia link, describes a case of supposed cannabis-induced schizophrenia in a teenager. At age 15, he became a heavy cannabis user at age 17, probably to treat his symptoms. A few years later, at age 20, he was finally diagnosed. Halfway through his prodromal symptoms, he began using cannabis to treat his illness.

I had a good friend recently who was a paranoid schizophrenic. He was 28 at the time and had apparently had the illness since he was 20 or so. He had not yet been diagnosed.

Hence the cannabis-schizophrenia link is said to be merely kids in the prodromal phase seeking relief for a condition that they are going to develop soon anyway and cannabis is not implicated in the disorder. This is always possible, but new research is suggesting that this is not the case.

With the new research, it is looking more and more like teenagers need to stay away from cannabis period. If they wish to use it, they should wait until age 19-20 or even better yet, age 21 when all cannabis-schizophrenia risk is gone.


Earleywine, Mitch. 2002. Understanding Marijuana: A New Look at the Scientific Evidence (pp. 149-150). New York: Oxford University Press.

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24 thoughts on “Cannabis and Schizophrenia Redux”

  1. “A recent study found that adults who started using cannabis before age 17 (16 or younger) had smaller brains overall, had less grey matter (fewer brain cells) yet more white matter (connections between neurons) (Earleywine 2005)”

    Im skeptical. It appears to be the case that non whites and non asians use pot more. They have smaller brain sizes.

    Also, because of DARE education, the smarter kids tended to not use drugs, and only use them once they read enough to believe that pot was not dangerous, while the dumb kids just wanted to get high.

    I do not know if the man corrected for gender. Females have smaller brains than men, and more white matter than average. If he compared the total marijuana users brain, with a male average, his result is trivial.

    Overall, there are *FAR* to many unknowns to get *ANY* conclusions from this cursory understanding of the mans methods. From the looks of it, his result can be explained by simple statistical messups.

    Also,”This psychiatrist posits that cannabis is causing schizophrenia”

    Many people who i knew who tried cannibus, also did drugs like LSD and other drugs, that has a known effect on psychosis. That may explain the result

    “The risk is greatest the younger you start”

    Well, kids who do not understand DARE, who come from dumb or mentally ill families, are all more likely(probably) to use drugs early compared with affluent families.

    All of these results appear to be explainable partly by simply the backgrounds of the people who use the drug.


  2. That, and kids who develop mental illnesses early naturally, are probably more likely to turn to drugs.

    1. That’s the self-medication theory. It’s a very good theory. If you look around the stories about people with schizophrenia, they often had symptoms for 5-10 years before they even got a dx. And at some point in that period, they started using cannabis and other drugs heavily to self-medicate.

      It’s not causing it really. Schizophrenia seems to be caused by massive brain damage, and cannabis causes little if any damage to the adult brain anyway.


    It seems that schizophrenics and pot smokers have a thing in common. They both tend to believe that “the system is lying to us” (at least thats what I see)

    It does not surprise me that that type of personality is more likely to develop symptoms of schizophrenia.

  4. Overall, since there are so many flaws with the studies, that can be largely explained by just the backgrounds of the people who end up using these illicit drugs, I can draw no conclusion.

    1. One thing I know FOR SURE is that heavy cannabis use brings on schizophrenia earlier than it would have come on ordinarily. On average about 7 years earlier. Also, cannabis seems to really worsen the course of schizophrenia for many people. However, some others get better on it.

    2. Well, perhaps its due to a reinforcement of personality types, rather than the actual effects of the drugs.

      For instance, if several people who lean right have a discussion, they will tend to move MORE right, since there are more arguments for right than left.

      There may be a reinforcement of personality types that are similar to schizophrenia. If these people who lean towards that, hang out with each other, the mental pathways may be reinforced. As heavy users are even more likely to believe “the system is lying” this may be reinforced.

      Well, I don’t have data, so im really only speaking in uncertainties. I would like to look into this more…which i will.

      Say, depressive types hanging around depressives become more depressed, outgoing types hanging around outgoing become more euphoric. People with unstable moods, only get worse by hanging out with people who have unstable moods.

      Maybe people who lean crazy, only get worse by hanging around the type of people who lean crazy, and smoking pot and discussing things with them, reinforces this

    3. That, and maybe this drug actually does help with some symptoms. However, the mental distrust that comes along with that, outweighs the potential benefits of the drug.

      Like, I made the right decision by making a crazy move. This crazy thought process becomes reinforced, getting more craziness, which requires more pot.


    4. Thing is, schizophrenia is not just folks thinking in a different way that can be cured by not thinking in that different way anymore (changing the way that you think). There is growing evidence that in schizophrenia your brain is well and truly fucked. IOW, in schizophrenia, there are massive problems with the brain = the brain is seriously damaged in schizophrenia.

      So, your brain is not going to get damaged by this just by hanging around people and talking about stuff. I mean I could talk about weird stuff til the cows come home and it’s not going to physically change my brain.

  5. Well…I do draw a similarity between antidepressants and pot.

    Antidepressants seem to be more dangerous for teens than adults.

    So, although I can’t draw any strong conclusion from these studies, I can compare these mind-altering substances together.

  6. Just wondering if pot ever helps with schizophrenia.
    I have 2 sons that think we should experiment with different strains to see if any would help their brother. Their brother has not had much help with the anti-psychotics that carry so much risk and side-effects. He is 26.

    1. It definitely helps some of them. Strains that are heavy in CBD might help, since CBD is proven to be an anti-psychotic. Strains heavy in THC would probably make him worse. You’ve got nothing to lose, might as well try.

      If it consistently makes him worse though, you might as well give it up.

      I am very sorry to hear about your brother. This is a terrible illness all right.

  7. ” thing I know FOR SURE is that heavy cannabis use brings on schizophrenia earlier than it would have come on ordinarily”

    That, or maybe people who are heavy users, are even crazier than people who tend to be light users, and want more self medication. These crazies would necessarily tend to get fullblown symptoms faster than other users or nonusers.

    1. The problem is that we see over and over the schizophrenics are pretty well stabilized and then they get some weed and start smoking it and they relapse quickly and hard. It’s quite clear that the weed causes a hard relapse in a lot of them.

      But it makes some of them better.

  8. Heavy users may be extremely stressed in their everyday lives.

    John Nash blamed his schitz on the large stressed he experienced.

    Maybe both this heavy use, and the schitz, are ultimately linked to an underlying stress, which increases both

  9. man, theres so many critiques coming to my head.

    Heavy pot smokers cannot admit to that, generally, to the average person, and they cannot go to a job interview smelling like that.

    So, they may have a larger stress in interacting with daily people, since they have to hide their daily habits.

    They also probably cannot find a job, and this stress also contributes to their problem. The lower short term memory contributes to the greater stress.

    They may hang out with other cynical people dissatisfied with the world. Mental illness, and stress from this, and from interacting with other people who are the same, may be a vicious cycle.

    So, Im not convinced that pot leads to schitz directly. I think its more likely that pot

    1. Leads to changes in personality, which lead to greater underlying stress, which then contributes to mental illness

    2. A negative social circle, dissatisfied with the world, may inadvertently discourage improving oneself.

    3. A relative poverty increases daily stress, and decreases ones general social status, which leads to mental illness(The columbine kids were not popular)

  10. “The problem is that we see over and over the schizophrenics are pretty well stabilized and then they get some weed and start smoking it and they relapse quickly and hard. It’s quite clear that the weed causes a hard relapse in a lot of them.

    But it makes some of them better.”

    Well, if thats the case, than it seems that weed overall has no effects. If there are so many examples and counterexamples, weed is probably seen as a scapegoat, that has no direct effect.

    Like antidepressants. They don’t work, some doctors end up believeing they worsen patients, some believe they make them better, when overall, they tend to do nothing about depression.

  11. That, and many schitz who are NOT on pot relapse anyways.

    So, randomly select 40 schits, give 20 pot, have 20 take none.

    In both groups, you are going to see a relapse, and in both groups, you are going to see people getting better.

    To determine the effects of pot, you have to do this experiment, and see if those who take pot..and do nothing else differently, relapse at a different rate.

    Has a study like this been done? That would pretty convincingly show the effects of the drug.

    1. They have been thinking about doing this study, but there are ethical implications. They’ve given pot to schizophrenics in the lab, and it makes a lot of them acutely worse on a single dose.

    2. Lol @ ethical implications. This study would, in the long run, benefit schizophrenics far more than the immediate potential negative effects on the participants.

      Hmm…do you have the experiment data?

  12. You have to remember that cannabis is not the same as it was. In Britain, a lot of people smoke super-skunk cannabis, which has lots more THC than the stuff the hippies were smoking in the sixties and seventies.
    I’ve tried this stuff, and it makes me very edgy and paranoid. I am absolutely 100% certain that if I smoked skunk regularly I would become mentally ill. The standard strength stuff just makes me lethargic, which is bad enough.

  13. Isn’t the reason for these ailments due to the lack of cannabis consumption over the past few generations?

    “Ignorance is plainly not knowing, stupidity is choosing to remain ignorant.”

    When will the time come when we choose to understand our humanity and come to grasp that no longer the people of the United States of America will continue to be persuaded by words such as “illegal, dangerous and addicting narcotics…etc?” Before we get in a rush (as we did during prohibition) we should remember those words prescribed above, are mere words we as humans created. And as all things we create, problems always seem to linger close behind.

    What exactly does a politician know about the medical sciences? Could any representative please describe to the American people (and not to mention the world) how 76 years ago the population was lied to about a substance that grows naturally and could have possibly very well prevented cancer(‘s), Alzheimer’s, M.S, and multiple other ailments we as humans are seeing an inclination of, not declination.

    Who was paying attention in the last paragraph? Did you look at the URL yet? Well basically this; We were sentenced a slow and painful death by our forefathers that will gradually kill off all of humanity because we faithfully neglect our body’s at the request of the government.

    Overall, my advice for people is to educate yourself before trying to explain the “M” word to people. You’ve seen the movies, those depictions of weak people who can not comprehend truth when they see it because they have been lied to all their lives. It is not their fault, some people have fears and some people conquer fear. What do “they” say again? Oh yeah, Never believe what “they” tell you.

    I would also like to call out all politicians to describe the Endocannabinoids System and how when neglected people are more susceptible to Cancer, Migraines, I.B.S, M.S, Alzheimer’s, rambling…

    “Quite surprisingly, the Endocannabinoids system has an all-pervasive role in maintaining homeostasis (biochemical balance). All living creatures suffer from a common biochemical imbalance, we are all aging.”

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