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(27,509 posts)
Sat Dec 28, 2013, 03:32 PM Dec 2013

Harvard: Marijuana Doesn’t Cause Schizophrenia


Harvard: Marijuana Doesn’t Cause Schizophrenia
Reviewed by John M. Grohol, Psy.D. on December 10, 2013


The new study is the first family study that, according to the researchers, “examines both non-psychotic cannabis users and non-cannabis user controls as two additional independent samples, enabling the examination of whether the risk for schizophrenia is increased in family members of cannabis users who develop schizophrenia compared with cannabis users who do not and also whether that morbid risk is similar or different from that in family members of schizophrenia patients who never used cannabis.”


The researchers recruited 282 subjects from the New York and Boston metropolitan areas who were divided into four groups: controls with no lifetime history of psychotic illness, cannabis, or any other drug use; controls with no lifetime history of psychotic illness, and a history of heavy cannabis use during adolescence, but no other drug use; patients with no lifetime history of cannabis use or any other drug and less than 10 years of being ill; patients with a history of heavy cannabis use and no other drug use during adolescence and prior to the onset of psychosis.

Information about all first-, second-, and third-degree relatives was obtained, as well as information about any other relative who had a known psychiatric illness. This resulted in information on 1,168 first-degree relatives and a total of 4,291 relatives. The study gathered together information regarding cannabis use, and family history regarding schizophrenia, bipolar disorder, depression and drug abuse.


“While cannabis may have an effect on the age of onset of schizophrenia it is unlikely to be the cause of illness,” said the researchers, who were led by Ashley C. Proal from Harvard Medical School.

“In general, we found a tendency for depression and bipolar disorder to be increased in the relatives of cannabis users in both the patient and control samples. This might suggest that cannabis users are more prone to affective disorders than their non-using samples or vice versa.” Future research is needed to understand this relationship.

Drug abuse also appears to have an important genetic component.


6 replies = new reply since forum marked as read
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Harvard: Marijuana Doesn’t Cause Schizophrenia (Original Post) bananas Dec 2013 OP
Good grief, Carruthers! intaglio Dec 2013 #1
would you mind x-posting this in the drug policy forum? RainDog Dec 2013 #2
I'd rather you or someone else do it. bananas Dec 2013 #4
okay. I posted it. RainDog Dec 2013 #5
Kicked and recommended. Uncle Joe Dec 2013 #3
It makes it unnecessary...ha-ha-ha!! Bill USA Dec 2013 #6


(8,170 posts)
1. Good grief, Carruthers!
Sat Dec 28, 2013, 05:06 PM
Dec 2013

Next thing you know they'll be saying reefer madness doesn't exist!

/purient twit


(27,509 posts)
4. I'd rather you or someone else do it.
Sun Dec 29, 2013, 03:00 PM
Dec 2013

There are several groups this could be posted in - drug policy, science, the two mental health groups, cooking & baking, etc.


(28,784 posts)
5. okay. I posted it.
Sun Dec 29, 2013, 03:04 PM
Dec 2013

This study matches with meta analysis done on all schizophrenia/cannabis studies and aligns with Roger Pertwee, the leading pharmacologist in the UK who studies cannabis. He says what this study says.

Good to see that more research is being done.

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