nos-trum. pronunciation: \nos'-trum\. noun. Etymology: Latin, neuter of noster our, ours.
1. a medicine of secret composition recommended by its preparer but usually without scientific proof of its effectiveness.
2. a usually questionable remedy or scheme.
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Sunday, March 6, 2011

STUDY: Psychosis Symptoms More Likely In Marijuana Users

Two studies this year showed increased risk of symptoms of psychosis after adolescent marijuana use.  The most recent was a better study, but not definitive.

Although the legalization crowd will criticize the studies, and their opponents will trumpet them, we haven't heard the last word on whether marijuana use among teenagers has anything to do with mental health, except as an "association" between two variables.  Previous studies, showing increased rates of schizophrenia and other mental health issues, have been criticized for being poorly controlled.

This week's study, appearing in the British Medical Journal, enrolled subjects age 14-24 who had not used marijuana before (first caveat:  "self-reported" non-use), and followed them for 10 years.  Those who subsequently became users had higher incidence of psychotic symptoms. [see here for an editorial on recent studies.]

As Nostrums readers know, the association of an exposure (marijuana) and symptoms (psychosis-type) doesn't mean that one caused the other.  It could just as likely be explained by an unknown variable shared by those at risk, or simply that people who are likely to develop psychotic symptoms are more likely to start using marijuana.

In designing the experiment, it was left up to enrolled subjects whether they initiated substance use or not.  From the perspective of experimental design, clearly this isn't random, or blinded.  And I can't think of a way to make it so.

That the risk of symptoms of psychosis increased the longer the person smoked is interesting, but doesn't necessarily imply a dose-effect (i.e., the more you inhale the worse you get). 

But you have to give the researchers some credit.  They compared users and non-users for differences in gender, socio-economic group, age, other drugs, and other health problems.  No differences were found.  This means the higher risk of symptoms of psychosis can't be explained by being poor, or male/female, or older, etc., the usual confounding variables.

I'm not a fan of substance use of any kind.  And smoking any plant probably entails similar lung risks (I'm not aware of any useful research that looks at lung cancer or emphysema risk in marijuana smokers).   But the science isn't complete.

The fur will fly over this research, and we are marginally closer to defining harmful effects, but the fat lady hasn't sung.

Doc D

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