Study suggests Cannabis does not cause Psychosis/Schizophrenia

[mgrady3]

from Schizophrenia Research - The Official Journal of the International Schizophrenia Research Society

"A controlled family study of cannabis users with and without psychosis"

http://www.schres-journal.com/article/S0920-9964%2813%2900610-5/abstract

abstract:

Cannabis is one of the most highly abused illicit drugs in the world. Several studies suggest a link between adolescent cannabis use and schizophrenia. An understanding of this link would have significant implications for legalization of cannabis and its medicinal value. The present study aims to determine whether familial morbid risk for schizophrenia is the crucial factor that underlies the association of adolescent cannabis use with the development of schizophrenia.

Methods
Consecutively obtained probands were recruited into four samples: sample 1: 87 non-psychotic controls with no drug use; sample 2: 84 non-psychotic controls with cannabis use; sample 3: 32 patients with a schizophrenia spectrum psychosis with no drug use; sample 4: 76 patients with schizophrenia spectrum psychosis with cannabis use. All cannabis using subjects used this drug during adolescence, and no other substance, with the exception of alcohol. Structured interviews of probands and family informants were used to obtain diagnostic information about probands and all their known relatives.

Results
There was an increased morbid risk for schizophrenia in relatives of the cannabis using and non-using patient samples compared with their respective non-psychotic control samples (p=.002, p<.001 respectively). There was no significant difference in morbid risk for schizophrenia between relatives of the patients who use or do not use cannabis (p=.43).

Conclusions
The results of the current study suggest that having an increased familial morbid risk for schizophrenia may be the underlying basis for schizophrenia in cannabis users and not cannabis use by itself.

Perhaps someone more in tune with this field of study could comment on this journal - I am not familiar with it with regards to its legitimacy or calibre of research but none the less it is an interesting read

PS. the title I chose was taken from another website that linked to the article.

 

[rhizome]

I always understood the research as saying that cannabis, while not causing schizophrenia, was associated w/ earlier emergence of symptoms- In other words, if you weren't eventually going to display symptoms, cannabis wasn't going to make you schizophrenic, but if you were eventually going to become schizophrenic, cannabis could trigger earlier emergence of symptoms.

Generally, earlier emergence of symptoms is predictive of more severe illness over the lifespan, but I'm not aware of research to determine if this applies to folks whose first emergence of symptoms was , at least temporally, w/ cannabis use. It could well be that cannabis triggers early emergence w/o deepening lifetime symptoms.

Certainly, cannabis doesn't cause schizophrenia in anybody who wasn't going to get it anyway. It might or might not worsen symptoms in folks who were going to get them anyway.

 

[mgrady3]

^^ That is the statement I have normally heard as well and this article seems to generally agree with that statement:

The results of the current study, both when analyzed using morbid risk and family frequency calculations, suggest that having an increased familial risk for schizophrenia is the underlying basis for schizophrenia in these samples and not the cannabis use. While cannabis may have an effect on the age of onset of schizophrenia it is unlikely to be the cause of illness (Compton et al., 2009, Galvez-Buccollini et al., 2012).