Does Marijuana Cause Schizophrenia?

Repost from the old site.
One of the longstanding arguments against the use of marijuana is that is causes mental illness, in particular psychosis. For a long time, cannabis was said to be associated with a particular entity called “cannabis psychosis”. This entity has not been proven to exist.
Cannabis has also been said to be associated with depression and anxiety. Some people do experience anxiety when they use cannabis. In many cases, they used it for some time before an anxiety reaction started. A cannabis panic or “paranoid” reaction is quite common amongst all types of cannabis users. Generally, users who start to regularly get panic reactions tend to stop using the drug.
Anecdotally, many persons report relief from anxiety, depression, tenseness and anger from the use of marijuana. A friend of mine who was in jail for marijuana said he met many angry prisoners who used marijuana to reduce their anger. I known young males who are chronically “hyper” – tense, restless and on the verge of anger. Regular marijuana use works well to completely alleviate this condition.
In recent years, some frightening studies have come out connecting cannabis to psychosis, in particular to schizophrenia. On the surface, there would not appear to be much grounds for alarm. As you can see in my previous review on the subject of cannabis and brain damage, heavy use of cannabis, of all the intoxicating drugs, seems to be easiest on the brain.
This does not mean that it has no effects on the brain at all, but instead that heavy use of all of the other intoxicants is harder on or riskier to your brain than heavy use of cannabis.
Since heavy cannabis use is so much easier on your brain than heavy use of anything else, how is it then that cannabis should be associated with schizophrenia, while the other more harmful drugs are generally not? This is a bit of a mystery.
Promoters of the pot-schizophrenia link have suggested cannabis’ effect on the dopamine system – that is, it releases dopamine. Yet almost all drugs release dopamine, including alcohol, cocaine, methamphetamine, etc. In fact, coke and speed are far more dopaminergic than cannabis. Truth is that anything pleasurable releases dopamine – sex, chocolate, a good movie.
Animal models have not been particularly helpful in determining the relationship of cannabis to mental illness.
One recent animal model showed that not only did cannabis cause mice to actually sprout new neurons in the hippocampus, but it also reduced measures of depression and anxiety. Opiates, tobacco, alcohol and cocaine all reduce neurogenesis in the hippocampus. The reduced depression and anxiety seemed to be caused by the neurogenesis. Cannabis also protects mice against brain cell death caused by alcohol.
There is also evidence that cannabis is protective against the neurotoxic effects of stroke and head injury. Further evidence shows that cannabis is effective in slowing the progression of various neurodegenerative diseases such as Alzheimer’s, MS, Parkinson’s, and ALS (Lou Gehrig’s Disease).
Given the evidence that cannabis does not seem to do much bad to your brain, and if anything seems to be neuroprotective and even neurostimulatory, it seems odd that this drug should be connected with such a devastating brain disease as schizophrenia.
Nevertheless, the evidence seems to be there, and it is quite frightening to look it over. The initial study was an elegant analysis of Swedish military recruits in 1987.
The increased risk was on the order of 4.5 times for those using by age 15, but down to 1.6 times for those using by age 18. The increased risk was decreasing rapidly. Let’s extrapolate to ages 16 and 17: Age 15: 4.5 X. Age 16: 3.7 X Age 17: 2.65 X. Age 18: 1.6 X. At that rate, all increased risk would have evaporated for users who wait until they are age 19 until they start using.
Since the Swedish study, the evidence has piled up. Still, despite the scary and numbing evidence, there is not yet any evidence that cannabis causes schizophrenia de novo. Instead, it appears to be interacting with some already existing risk factor.
This page is a good repository for the numbing evidence on this score.
However, that site has some serious problems.
They are finding increased risk of schizophrenia from everything from “being too introverted and being alone too much”, emigrating to a new country – up to 4X increased risk, having an unpleasant and unstable home life as a child, experience – social adversity – four or more episodes of “abuse” increased risk by 2.7X, living in a city (3X increased risk), especially an inner city (as opposed to the country), or being vulnerable to depression or anxiety.
In order to avoid schizophrenia, according to the site, one would have to never go live in a new country, never spend a lot of time alone or be an introvert, never move to a city or an inner city or never grow up in one, be robust in handling stress, experience little social adversity, and somehow assure that one had a happy and stable home life as a child.
At some point, you just have to live your life and these kind of “risks” be damned. Personally, I am dubious that any of these things actually contribute to schizophrenia.
A person slowly developing schizophrenia over years tends to spend a lot of time alone, become introverted, move to a major city (often the rundown inner city part), wander around the country or parts of the globe, experience a lot of social adversity and handle stress quite poorly as the disease slowly unfolds.
Their relatives often show various degrees of the illness themselves and this probably accounts for the problems in childhood experienced by mildly effected parents. Either that, or the person at risk of schizophrenia is already odd, hostile or combative, and this causes a poor parental relationship.
Even if cannabis did increase the risk of schizophrenia, there seems may be an age effect. Robin Murray found that first use at age 15 increased the risk of schizophrenia by 4 times, while by age 18, the risk had dropped to 1.65. By this trend, one assumes that at some point after age 18, the risk would drop to zero. Assuming the risk is real, it could be substantially ameliorated by avoiding cannabis until one is 18.
In general, most studies found about a doubled risk of schizophrenia from cannabis use. It is interesting to note that chronic heavy drinking was even more of a risk to psychosis than heavy cannabis use, increasing the risk by four times.
It has become clear in recent years that schizophrenia, when occurring over a period of years, is correlated with serious damage and disruption to the brain in a wide variety of areas and manners. The notion that a meager drug like cannabis could actually cause such dramatic dysfunction and damage is ludicrous.
The only thing that could possibly be happening here is cannabis triggering, or setting off, a cascade that begins the neurodegenerative process known as schizophrenia.
The pot-schizophrenia theory was recently blown up again by a truly absurd study. An MRI study showed that subjects given THC showed reduced activity in the inferior frontal cortex. This area controls inappropriate emotional and behavioral responses to situations. The more the activity was reduced here, the more paranoia the subjects experienced.
Somewhat bizarrely, the study claimed that pot-induced “paranoia,” which most users are familiar with, is synonymous with “psychosis.” They said that 50% of the users “became psychotic” and experienced schizophrenia-like symptoms. That is obviously idiotic. If that is psychosis, then every marijuana user I have known (thousands) have been psychotic many times.
The major problem with all of the studies showing a link between pot and schizophrenia is that we should have seen an explosion of schizophrenia in the West during the 1960’s and 1970’s. Instead, the rate was flat or even declined.
Advocates of the pot-schiz link such as Murray have all sorts of reasons why either rate has actually gone up when we found it didn’t, or it’s going to go up in the future, or finally, that even heavy pot use by millions of citizens will only increase the rate of schizophrenia by 14%. This absurd and totally unproven “14%” figure is now being bandied about by the media (see below).
This study from Australia concluded that since the incidence of schizophrenia has not risen with the explosion in cannabis use, cannabis cannot be said to cause schizophrenia. Instead, the study said cannabis appears to be triggering it in people who would have ended up schizophrenic anyway. However, cannabis use may worsen the course of schizophrenia in those who already have it.
The study was unable to conclude that cannabis use brings on schizophrenia quicker in those who would develop it anyway, since they found no trend in decreasing age of diagnosis, even with the explosion in cannabis use in recent years. However, this study did find that cannabis-using schizophrenics developed symptoms sooner than those who did not use it.
On the other hand, this may be explained by the very common phenomenon of heavy use of cannabis during the prodromal phase of schizophrenia. Another study suggested that cannabis use may be causing schizophrenia in people who would not otherwise develop it, but the lack of increased diagnosis would seem to argue against that.
Yet another Australian study concluded that cannabis precipitates and worsens schizophrenia in those who would have developed it anyway.
Much of this data is from a group of psychiatrists in London (centered around Robin Murray – see above) who are convinced that marijuana is increasing the incidence of schizophrenia in the UK.
They have produced data showing that the rate of schizophrenia has gone up in their inner-city neighborhood in recent decades. However, that increase is at odds with studies done over much of the rest of the world in recent decades.
The same researchers produced another “definitive” study that “ends the debate” about whether or not marijuana causes schizophrenia. It reviews a number of studies and shows that every study does find increased psychosis with increased marijuana use. It then predicts that 14% of all cases of schizophrenia in the UK are being caused by pot use. This conclusion is unwarranted.
First of all, there is indeed an association between pot use and schizophrenia (in my opinion, especially under age 18 and particularly under age 16). However, as you can see below, the rate of schizophrenia in general has been either flat or declining all through the cannabis epidemics of the past 40 years in the West.
Therefore, it is premature of the UK researchers to claim as yet that pot is causing 14% of schizophrenia cases in the UK.
A paper out of Micronesia dated 1993 noted that schizophrenia had increased dramatically in the previous 20 years. There had been an attendant increase in the use of marijuana and other drug use.
The Australian study above, one of the best studies done to date, completely rejected the notion that cannabis causes schizophrenia in persons who would otherwise not develop it, but did suggest that cannabis use may bring on schizophrenia sooner in those who were going to develop it anyway.
Heavy cannabis use does seem to be particularly problematic in early adolescence. Kids that age should not be using cannabis anyway.
The Australian study also suggested that cannabis worsened the prognosis of schizophrenia, but that the effect was not a large one. Studying this variable is difficult since the younger one is when schizophrenia comes on, the more likely the person is to relapse, and young people are the most likely to be cannabis users.
So cannabis use and relapse to schizophrenia are going to be co-occurring due to age alone. Nevertheless, there seems to be good evidence that schizophrenics need to stay away from this drug.
The one hypothesis that shines through most clearly in all of these studies is that schizophrenics tend to be more likely to use cannabis, and more likely to use it heavily, than non-schizophrenics. In other words, simply being schizophrenic increases the likelihood of cannabis use and dependence. We can surely agree with this theory – it’s not controversial at all.
Along the lines of the Australian study, we can look at tobacco use and lung cancer. As cigarette smoking skyrocketed, lung cancer went through the roof. As smoking declined, lung cancer rates also declined.
No such picture is being seen with cannabis and schizophrenia.
Another recent study is getting a lot of media play with a totally unwarranted pot-schiz link. It found an altered development of the arcuate fasciculus, a bundle of fibers connecting the Wernicke’s and Broca’s Areas of the brain, one involved in the production of language and the other involved in the reception of language. Photo of the arcuate fasciculus is here, and a schematic is here.
Damage to the arcuate fasciculus is associated with a particular type of aphasia where language can be produced and comprehended well, but if you say something to the sufferer, they cannot repeat what you just said. The arcuate fasiculus is still developing in early adolescence, but it is not known if it continues growing in through late adolescence.
Lower volume was seen on the left side of the arcuate fasiculus in adolescent heavy marijuana users. In schizophrenia, there is reduced volume on both the left and right sides of the arcuate fasiculus. Defects in the arcuate fasiculus in schizophrenia have unknown significance, but the structure is abnormally activated, along with some other areas, during auditory hallucinations.
Excessive activation of the arcuate fasiculus associated with auditory hallucinations would not likely be caused by a reduced volume to the structure. With reduced volume, there would probably be less activation.
Damage to the brain in schizophrenia, as noted above, is quite vast and covers widely disparate areas of the brain, involving multiple structures.
Some areas are abnormally activated, while others are abnormally dormant. There are problems with various neurochemicals in the brain and receptor alterations in the cells themselves.
In short, schizophrenia is a disease caused by massive damage to the brain. One recent study likened it to a forest fire in the brain.
The problems in the arcuate fasiculus are but a tiny subset of the massive organic damage of schizophrenia. The fact that the arcuate fasiculus may be damaged by heavy cannabis use in adolescence is disturbing, but it hardly proves that such use causes schizophrenia, because schizophrenia requires much more damage than that.
Further studies using DTI found no abnormalities whatsoever in any part of the brain. In fact, if anything, adolescent cannabis users tended to have larger brains, with more cells (white matter) than the controls.
That doesn’t mean that using cannabis in adolescence makes you smart, but it surely rules out significant organic structural brain damage, and it does add interesting weight to the neuroprotective and neurostimulatory papers above.
Furthermore, many reports of “cannabis psychoses” do not appear to be psychoses at all. This preposterous report of two cannabis psychoses, published in a respected peer-reviewed journal of all things, is illustrative.
Looking over the paper, Case 1 appears to have just gotten really stoned. If that’s “cannabis psychosis”, then I’ve been “psychotic” on cannabis hundreds of times, and I must have witnessed thousands of other “cannabis psychoses”.
Case 2 is a bit more difficult, as he became suspicious of the testers at one point. It’s well known that cannabis users can feel frightened and even “paranoid.” Lord knows, I experienced it many times myself. However, the man merely felt that the testers were “concealing problems” from him. That really does not qualify as a paranoid delusion.
The world is full of suspicious people. At times, I’m pretty suspicious and wary myself, for good reason, I would say. The vast majority of people even with pathological suspicion or paranoid ideation are not suffering from paranoid delusions.
Furthermore, the questions that are asked on questionnaires of cannabis psychosis are dubious. “Most people cannot be trusted.” Well, if you live in the ghetto or the barrio, that’s a damn good attitude!
“Sometimes it seems like people are looking at me and talking about me.” Look, as you go about your business day to day, it’s quite possible people may take notice of you in one way or another.
At times people may indeed talk about you, sometimes within hearing distance. It’s hard to say whether they are talking about you in a friendly way or not. Sometimes they may seem friendly; other times not, but mostly of the time, they will probably just seem neutral.
A typical psychological questionnaire will ask you questions about many of these things. If I answer yes to any of them, it gets chalked up to “paranoia.” I know because I have taken these tests.
If you act strange in any way, people are much more likely to stare at you and even talk about you behind your back. So if everyone who acts odd enough to get stared at is hip enough to recognize the obvious, that means they have a paranoid psychosis?
There are indeed folks out there who seem to others to behave strangely. In our society, they may be called nerds, nervous, weird, or shy. Perhaps in Japan they fit right in. There are folks who live alone, never marry and even folks who never date. I’ve run across quite a few “odd” folks in my life who were not psychotic in any way. Most were not even mentally ill.
Now, I can assure you that these folks are going to get stared at from time to time, and people will even talk and whisper about them behind their back. If they happen to be self-aware enough to notice this, does this mean that they are paranoid?
In conclusion, there is some frightening stuff out there about pot and schizophrenia. At the moment, it should be read with caution. A judicious approach would be for adolescents to wait until they are at least 18 and possibly even older until they start using cannabis.
The available evidence indicates a rapidly declining risk towards the end of adolescence that presumably declines to zero increased risk at some point probably soon after age 18.
Even there, though, the Swedish study found that heavy users by age 18 were six times more likely to develop schizophrenia than non-users. So if you are going to use cannabis heavily, you should wait until you are at least 19, and possibly even older.
Prudent cannabis users will wait until they are at least 19 and then not use the drug every day. Those using or beginning to use the drug later in life, for instance me at age 50, surely must have zero increased risk of psychosis. Further research will presumably elucidate some onset age at which use of cannabis is not associated with any increased risk of schizophrenia.
I would also like to recommend a similar area of research: medical cannabis. There are many medical cannabis users now in various countries. Many of them are older people, as these are the ones who tend to be more injured or ill in life.
An interesting study would determine precisely how many of these medical cannabis users are developing schizophrenia. I have not heard of a single case so far. The number of cases must be quite small.
To add a personal link:
I used cannabis for about 22 years off and on since 1973.
All these psychiatric reports anger me because at my age and with my mental state, cannabis use dramatically improves my mental health. Many others report similar benefits. The notion that cannabis always or almost always causes deterioration of mental health is utter nonsense, and I am getting sick and tired of hearing of it.
Sure, it’s bad for some people, but look around the Net and see how many people are using it to treat anxiety disorders, eating disorders, mood disorders, etc. Does it not stretch credulity to think that all of these people are just making stuff up?
All my friends were pot smokers, and many were potheads. I also sold drugs, mostly pot, for 14 years, never got caught (neither did the vast majority of my friends) and don’t regret a thing. Actually, being a dealer was kind of fun.
Not only did I never experience any psychotic symptoms while using cannabis, I have never experienced any while off of it either. Further, I have never seen one single case of psychosis attributed to cannabis, much less schizophrenia, and that includes probably thousands of pot smokers over decades, including hundreds of heavy users, many of whom used for many years.
Based on my own experiences, any risk of schizophrenia due to cannabis is not likely to be large.
I have known a few people with schizophrenia, but not many. I was good friends for about a year with a paranoid schizophrenic who heard voices much of the time until people told me to get away from him. He had only smoked pot a couple of times and did not like the drug.
I know of one schizophrenic, ill from an early age, who loved to smoke pot. But it made him a lot worse, so everyone tried to keep him away from it. Interestingly, his brother, surely at risk of schizophrenia, was a dealer and very heavy cannabis user for many years, never developed schizophrenia and was reasonably well-adjusted.
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158 thoughts on “Does Marijuana Cause Schizophrenia?”

  1. I have researched schizophrenia and discovered a link to marijuana use that nobody has ever put together. What causes schizophrenia? A buildup of free copper due to the atpb7 copper binding gene defect. The free copper builds up in the blood and if the blood brain barrier is intact the copper doesn’t enter the brain and cause schizophrenia. The THC in marijuana penetrates this barrier and leaves tiny holes behind. If people with this free copper in their blood smoke marijuana the free copper enters their brain and they get schizophrenia. The free copper is toxic and oxidizes adrenaline which creates adrenachrome. The adrenachrome makes them paranoid. The free copper is also a conductor of electricity and when it enters the brain it allows demonic entities, which consist of electromagnetic energy to reside in their brain and they start hearing voices. If you want to see an MRI image of a demon, google “face of the giant panda”. Japanese researchers discovered that when the copper is chelated out of the brain this image disappears from the brain and the psychosis is gone. Interestingly these demonic images won’t show up on cat scans, but MRI only, which shows me they exist in the electromagnetic spectrum that is invisible to the naked eye. The cure for schizophrenia is to get rid of the copper by taking zinc, which takes a while or get the TM copper chelating drug which is faster. Get rid of the copper you get rid of the demons, because they can’t reside in a brain without the free copper to live in. Look at the research of Carl C Pfeiffer and the 30,000 schizophrenics he cured with zinc or pipex pharmaceuticals work with the TM ammonium tetrathiomolybdate drug that they plan to use to cure schizophrenics.

  2. I’m 26 now… I smoked pot chronically without any problems since 14. Right on my 24th birthday…I smoked then couldn’t sleep due to auditory hallucinations…it was really clear and scary…I thought I had awesome super hearing or something because the voices were of my neighbors and family that were in their rooms n not in sight. I had vivid conversations with 3 or 4 at most until recently I heard a group of late partiers next door threatening to home invade me only to look next door and there is no party…I’m hearing clear songs in my head wich is cool but also creepy. I hear hate comments which no one else does. It gets worst at night and I can’t sleep…I’m losing my mind here folks. Please help. I saw the part about the %20 perecent increase in Micronesia…I’m micronesian…help please.

  3. My bf just got diagnosed with Schizophrenia in December. he had alot of stress weighing on him and he just snapped. He broke up with me telling me i deserved better and that I needed to find someone else but we had been together 3 years, i didnt want anyone else. thats when i started to pay attention something wasnt right. you could see it in his eyes and everything he said just sounded like lies. I got so bad for him that he took a whole bottle of sleeping pills and drove himself to the police station to turn himself in for something he didnt really do but in his mind he did. after hours and hours of interigation from the police and them trying to get him to convict himself someone finally realized something wasnt right and sent him to the hospital. it only got worse form there once in the hospital voices had convinced him that when the nurses tried to put his iv in that they were injecting him with aids…. mean while i was at work when all this happened and left early when his mother called me and had me panicked. i drove by and his car was home so i figured nothing to serious was going on until i got a text saying he was in the mental hospital and tried to kill himself. My heart sunk. i felt like i was going to vomit. how could the man that i love so deeply ever think about leaving me like that. (typing this is bringing tears to my eyes). I bawled and bawled for hours i didnt understand. my heart had litterally shattered. his mom thought it would be best if i didnt visit him yet due to the fact we were still broken up. after a day of him being on the meds and getting lots of sleep he needed he asked me to come up to visit. I called off work and went to see him. he finally looked like the bf i met 3 years ago. we got back together that very second. i never wanted to let go of him. he smoked weed for years on a regular basis. the main thing in our relationship was smoking together all the time. He swears up and down that drugs caused him to go crazy. now that he has quit he is a whole new person. i love him now more than i ever have before. I know alot of people smoke now a days but seriously if you start to feel like your having weird reactions quit before things really start to happen. he used to tell me all the time that he could hear angels when he smoked but i thought nothing about it. If you cant quit for yourself quit for the people who love you. I honestly dont know where i would be if he actually did commit suicide. Id probably be a drunk and depressed and never be going anywhere in my life. if smoking weed makes you paranoid or hear things or even just feel weird. please just quit. its not worth it at all.

  4. The vapour isn’t smoke, in order that it will not irritate your lungs or throat. It is essential to remember that vapor can often be more concentrated when direct inhalation is used. The bridge will be the raised center part covered inside the gray metal mesh.

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