Pubdate: Thu, 10 Mar 2005
Source: AlterNet (US Web)
Copyright: 2005 Independent Media Institute
Contact:  http://www.alternet.org/
Details: http://www.mapinc.org/media/1451
Authors: Bruce Mirken and Mitch Earleywine
Referenced: the study http://www.csdp.org/research/260Xoriginal.pdf

PSYCHOSIS, HYPE AND BALONEY

As the month began, the worldwide press jumped all over a study in the 
March issue of the journal Addiction purporting to show a causal link 
between marijuana use and psychosis. "Drug Doubles Mental Health Risk," the 
BBC reported. "Marijuana Increases Risk of Psychosis," the Washington Times 
chimed in.

Such purported links have lately become the darling of prohibitionists, but 
a close look at the new study reveals gaping holes unmentioned in those 
definitive-sounding headlines.

Before we look at the study itself, let's consider some basics: If X causes 
Y, it's reasonable to expect a huge increase in X to cause at least a 
modest increase in Y, but this has not been the case with marijuana and 
psychosis. Private and government surveys have documented a massive 
increase in marijuana use, particularly by young people, during the 1960s 
and '70s, but no corresponding increase in psychosis was ever reported. 
This strongly suggests that if marijuana use plays any role in triggering 
psychosis, that effect is weak, rare, or both.

For this reason, researchers should approach "proof" that marijuana causes 
serious mental illness with great caution. The researchers in this case, a 
New Zealand team led by David M. Fergusson of the Christchurch School of 
Medicine and Health Sciences, seem to have done just the reverse.

Fergusson's team looked at a group of 1,265 New Zealand kids who were 
followed from birth to age 25 and assessed at various points along the way 
for a variety of physical, mental and social problems and issues. At ages 
18, 21 and 25 they were assessed for both marijuana use and supposed 
psychotic symptoms. Having found a correlation with daily users reporting 
the highest frequency of psychotic symptoms, they then applied a series of 
mathematical models. These models are designed to adjust for possible 
variables that might confound the results and to assess whether the 
marijuana use caused the symptoms or vice versa.

Whatever model was applied, the correlation held up. But the reported 
"growing evidence" that "regular use of cannabis may increase risks of 
psychosis" depends completely on the validity of the underlying data, and 
those data raise some screamingly obvious questions.

Psychotic symptoms were measured using 10 items from something called 
Symptom Checklist 90. Participants were asked if they had certain ideas, 
feelings or beliefs that commonly accompany psychotic states. The 
researchers did not look at actual diagnoses, and the symptom checklist is 
not identical to the formal diagnostic criteria listed in the DSM-IV 
manual. Perhaps most important, they only used 10 "representative" items 
from a much larger questionnaire.

These 10 items focus heavily on paranoid thoughts or feelings, such as 
"feeling other people cannot be trusted," "feeling you are being watched or 
talked about by others," "having ideas or beliefs that others do not 
share." This presents a big methodological problem, because it is well 
known that paranoid feelings are a fairly common effect of being high on 
marijuana.

But the article gives no indication that respondents were asked to 
distinguish between feelings experienced while high and feelings 
experienced at other times. Thus, we are left with no indication at all as 
to whether these supposed psychotic symptoms are long-term effects or 
simply the normal, passing effects of marijuana intoxication. While it's 
possible the researchers had these data and didn't see a need to report 
them, the failure to do so is downright bizarre. It's like reporting that 
people who go to bars are more erratic drivers than people who don't, 
without bothering to look at whether they'd been drinking at the time their 
driving skills were assessed.

Even if these were long-term effects, the researchers seem not to have 
considered that what might be an indication of psychosis in other 
circumstances could be an entirely normal reaction for people who use 
marijuana. Consider: Someone using a substance that is both illegal and 
socially frowned-upon almost by definition has "ideas or beliefs that 
others do not share." This is not a sign of mental illness. It's a sign of 
a rational person realistically assessing his or her situation.

The same goes for "feeling other people cannot be trusted." Just ask Robin 
Prosser, the Montana medical marijuana patient arrested last summer on 
possession charges by the cops who came to save her life after she'd 
attempted suicide because she was in unbearable pain after running out of 
medicine.

Fergusson reports very little raw data, so we don't know which symptoms 
came up most often, or whether the differences in average levels of 
symptoms between users and non-users came from a few people having a lot of 
symptoms or a lot of people having a couple symptoms. The heavy-user group, 
with the highest levels of supposed psychosis, reported an average of less 
than two symptoms each. So it is entirely possible that the entire case for 
marijuana "causing" psychosis is based on marijuana smokers having the 
completely reasonable feelings that they have beliefs different from 
mainstream society and thus should be a tad suspicious of others.

"Proof" that marijuana makes you psychotic? No. Not even close. But don't 
expect the mainstream media to figure this out. 
- ---
MAP posted-by: Richard Lake