More threads by David Baxter PhD

David Baxter PhD

Late Founder
Schizophrenia risk for patients with cannabis-induced psychosis

Half of all patients treated for cannabis-induced psychosis may subsequently develop a schizophrenia spectrum disorder, reveal study findings that highlight the need for clinicians to recognize the prognostic significance of the condition.

The course of cannabis psychosis has been seen as benign by many experts, with symptoms thought to remit rapidly and full recovery to occur after stopping cannabis use.

Mikkel Arendt from Aarhus University Hospital in Risskov now reports that "subjects who experience psychotic symptoms that are not transient and lead to treatment seeking are at an extremely high risk of developing schizophrenia subsequently."

He told MedWire News that while temporary remission can be expected, schizophrenia can still develop some time later, often several years after cannabis-induced psychosis.

"I think that a cannabis-induced psychotic condition can often be seen as an early sign of the development of schizophrenia," he said.

Arendt and team collected information on 535 patients treated for cannabis-induced psychotic symptoms between 1994 and 1999 from national registry data.

During 3 years of follow-up, 44.5% of these individuals were diagnosed with schizophrenia spectrum disorders, and new psychotic disorders of any type, including bipolar and anxiety disorders, were diagnosed in 77.2% of individuals.

Such disorders were often delayed, occurring more than a year after seeking treatment for cannabis-induced psychosis in 47.1% of patients.

Arendt and team also found that people with cannabis-induced psychosis developed schizophrenia at a younger age than those without a history of the condition.

Among 2721 people with schizophrenia-spectrum disorders who had no history of cannabis-induced psychosis, the average age of schizophrenia onset for men was 30 years, compared with 24 years for those with cannabis-induced psychosis. Among women, onset occurred at the age of 29 and 33 years, respectively.

This suggests that cannabis use may hasten progression of schizophrenia, the researchers write in the Britsh Journal of Psychiatry.

"I think that professionals who encounter young people with cannabis-induced psychotic symptoms should offer advice to the patients and their relatives," Arendt commented.

"In addition, they should be followed closely by the treatment system, so intervention can be initiated as soon as possible if there are signs of schizophrenia.

"The earlier treatment is started the better the prognosis for the patients."

Br J Psychiatry 2005; 187: 510-515
That really scared me. I had a cannabis-induced psichosis with further developments after I quit consuming. Can anyone tell me how to "prevent" to have schizofrenia?


This suggests that cannabis use may hasten progression of schizophrenia

Would you help in interpreting the significance of this article.

Is schizophrenia a genetic disorder that may be latent in some people which can be triggered by the use of cannabis (or other factor) for that matter?

Can one conclude that cannabis use eventually leads to cannabis induced psychosis and if so what is the incidence of this happening?

How is a cannabis induced psychosis different from any other psychotic event?

How does this information impact a person who uses cannabis for (true) medicinal treatment under the supervision of a physician ?

David Baxter PhD

Late Founder
I think you have the basic idea, Steve. I think the best way to think of this is as a genetic vulnerability. You are born with (or it may also be possible to acquire at some age) a vulnerability to developing schizophrenia. various experiential, environmental, medical, possibly viral or bacterial stressors may then trigger the development of the illness in a vulnerable person, whereas without those triggers it is conceivable the person may remain asymptomatic. This is conjecture to a degree, of course.

In such a vulnerable person, moderate to heavy cannabis use may trigger (or hasten) the development of the full illness. It is even possible that even mild cannabis use may trigger the illness in particularly vulnerable individuals. I have seen such an effect for anxiety disorders and OCD with only one or two exposures to cannabis. On the other hand, non-vulnerable individuals may not have that reaction even with prolonged heavy use (although there would almost certainly be other negative consequences).

Other psychoactive street drugs may of course have a similar effect - it's not confined to cannabis by any means.

Modus.Ponens, to answer your question, not all drug-induced psychotic episodes are schizophrenia and not all are repeated. You might question the doctor who saw you during that episode for an opinion or see a doctor and ask for an opinion now. I would suggest, though, that having had one drug-induced psychotic reaction you should consider yourself at risk, and I would strongly advise against continued use.
Thank you Dr. .

I'v abandoned cannabis a long time ago. But in the last few months, I sometimes felt tempted to smoke it again. Now I defenetly lost that temptation! Erradicated! I have a real fear of schizophrenia. I just woke up from a nightmare that I think that was originated from reading this topic :(. And my aversion to taking medication is also big since I had already taken risperdal for some time and I felt numb. I don't want to be numb again...


what about stimulant induced psychosis? i have a boyfriend that has been taking dexedrine for years and he recently had an episode. he has calmed down a great deal since he's been off these meds. however, he has not let go of the old thoughts. those of being persecuted and surveilled.

he might have a genetic predisposition because his mother also had a psychotic episode when he was younger. however, it is hard to tell because there have always been drugs involved, and environmental influences. she takes all sorts of pills, in ways that do not seem legitimate.

do you think there will be permanent side effects? also, he's thinking about taking one of those anti-smoking medications like ziaban or wellbutrin. do you think these could affect his condition negatively? he has mentioned suicide in the past so i'm a bit worried.


David Baxter PhD

Late Founder
g-scared, his doctors are the only ones really in a position to determine what medications he needs.

However, as to the question of whether long term use or abuse of a stimulant such as dexedrine can induce a psychotic reaction, the answer is yes. This is not normally a concern when it is prescribed appropriately and used as directed in the treatment of ADHD. However, if in fact he does not meet the criteria for ADHD and/or if he was taking more than the recommended dosage and/or if he suffers from one or more additional conditions that might contraindicate the use of dexedrine, it is possible that his current psychotic reaction is at least partly a result.


Does anyone know if alcohol can also be a trigger for schizophrenia?

Also, how long does it take to come down from using amphetamines?
Perhaps I should have posted in addictions.

Hope I am not sounding too confused but I am just worried about someone and you may have noticed I haven't been on for a while.

Actually I could probably post in a few different places. I feel very anxious and depressed and don't know where to turn. Typing this is getting it out of my system a little. Thanks for listening. :( K9

David Baxter PhD

Late Founder
It's hard to know with certainty what can and cannot be a trigger for a first psychotic episode, K9, but I wouldn't rule out the possibility of alcohol abuse being a contributing factor. If the individual has also been using other substances such as amphetamines, the risks are likely increased.


David Baxter said:
It's hard to know with certainty what can and cannot be a trigger for a first psychotic episode, K9, but I wouldn't rule out the possibility of alcohol abuse being a contributing factor. If the individual has also been using other substances such as amphetamines, the risks are likely increased.

thanks for your reply David :) K9


K9. I haven't been around for a while for similar reasons. I would recommend that you look at this post if you have a friend that might be experiencing psychosis and addiction. It is a very difficult situation that I have been struggling with for quite sometime. I find that learning about it really helps though.

One point I found very interesting was a testimony by a girl, who was diagnosed as pre-psychotic, or something like this. I am speaking from memory, so forgive me if this is not completely acurate. In any case, as a preventive measure she was encouraged to sleep regularly, stay away from sugar and caffeine, and above all stimulants. These are all things my b/f loves and they contribute very badly to his condition.

I have also read a bit on schizophrenics that also suffer from alcoholism, in an attempt to self-medicate. Whatever the case may be I think your friend needs professional help if he is causing you to worry so much.
good luck,
ps- this is a link to a sibling's guide to psychosis. i am not a sibling, but i think that i've reacted very similarly to one in many ways, and that the advise has been very useful.,3055.0.html


g-scared, thanks for your reply and info.

I looked up that site you recommended and found it very interesting and informative. I have adult 'children' and this could also be of some use to
them. I have also been browsing and read your other post and hope all goes well for you. You have done all that you could to help him and now need to look after yourself.

Take care of yourself :) K9


To me, this just shows that people diagnosed with "cannabis-induced psychosis" are really just schizophrenia-spectrum, and were misdiagnosed.

I'm diagnosed right now with "Psychosis Not Otherwise Specified: Polysubstance Abuse," and yet after a month and a half completely clean, I'm still experiencing psychotic episodes.

It's certainly true that drugs can exacerbate psychosis; this has been proven again and again. But the idea that cannabis can induce psychosis in otherwise healthy people is not thoroughly tested, and this study appears to be evidence against it.

David Baxter PhD

Late Founder
I'm not sure I fully agree with your conclusion, textured, although I agree it's a possibility.

Obviously, not everyone who is a regular or even heavy user of cannabis develops a psychotic disorder, just as not everyone who is a regular or heavy tobacco smoker develops lung cancer. To me that suggests that some people are more vulnerable than others and that for those who are more vulnerable cannabis use can trigger a psychotic break.
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