What proportion of psychotic illness is due to cannabis?

Sep 29, 2009

In this week's PLoS Medicine, a team of researchers from Australia and the US, led by Louisa Degenhardt at the University of New South Wales, Sydney, makes the case for estimating the role that cannabis has worldwide as a risk factor for psychosis.

This estimation, says the team, will give an idea of how much impact cannabis has upon public health globally. The information in turn could be valuable for guiding health policymakers in deciding about health policies, services, and research.

The global impact of different diseases and risk factors upon population health is estimated by a high profile international research initiative called the Global Burden of Disease Project (http://www.globalburden.org/). Some of the risk factors that the project assesses are smoking, , obesity, and alcohol use. But in the past the project has not examined cannabis as a risk factor, say Degenhardt and colleagues, because of concerns that the evidence linking cannabis use to psychosis is too weak.

Degenhardt and colleagues examine the studies that have shown a link between using cannabis and developing psychotic illnesses such as . Based on the strength of this evidence, and on the fact that cannabis use is a potentially preventable exposure, they argue that the Global Burden of Disease Project should include cannabis as a risk factor. The authors review lines of evidence which suggest that cannabis may be a particular risk for those vulnerable to developing the illness. They propose to model multiple possible relationships between cannabis and psychosis, including models of poorer outcomes for those who have developed the disorder.

Researchers in Australia, for example, included cannabis in their national study of the impact of risk factors and diseases upon population health. In estimating the impact of cannabis, the researchers assumed that the evidence was good enough to show a link between cannabis use and psychosis, suicide, and car crashes. "Even after assuming that these relationships were causal," say Degenhardt and colleagues, "cannabis was not a major contributor to disease burden in Australia, accounting for 0.2% of all disease burden, which amounted to 10% of the total burden attributable to all illicit drugs."

"These estimates are important for public policy purposes," they say, "because failure to make them allows untested estimates to be offered in public policy debate."

The authors argue that if the international community does not estimate the global impact of cannabis use, there will be important consequences. "There will be a reduced public health, policy, or research imperative, since there will be no estimated burden."

On the other hand, they say that "if we do attempt to estimate burden, future work will examine the accuracy of our estimates and refine them as evidence accumulates. Debates may emerge and (hopefully) improvements made as new evidence supports or challenges the assumptions made.''

More information: Degenhardt L, Hall WD, Lynskey M, McGrath J, McLaren J, et al. (2009) Should Burden of Disease Estimates Include Use as a Risk Factor for Psychosis? PLoS Med 6(9): e1000133. doi:10.1371/journal.pmed.1000133

Source: Public Library of Science (news : web)

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frajo
4.2 / 5 (5) Sep 29, 2009
The global impact of different diseases and risk factors upon population health is estimated by a high profile international research initiative called the Global Burden of Disease Project. [...] Some of the risk factors that the project assesses are smoking, high blood pressure, obesity, and alcohol use. But in the past the project has not examined cannabis as a risk factor

Neither has the project examined poverty and hunger as risk factors upon population health. Strange. Or maybe not.
rubberman
5 / 5 (2) Sep 29, 2009
Why not just find out how many of the millions worldwide who seek, or are assigned psychiatric care have frequent cannibis use listed on their chart. Then compare that to the rest of the issues on the chart....then flush your theory down the toilet.

I'm not saying that over use of cannabis won't lead to mental issues. However, the list of things that will cause mental issues with over consumption is about the same size as the phonebook of a small town.....
cybrbeast
5 / 5 (2) Sep 29, 2009
the researchers assumed that the evidence was good enough to show a link between cannabis use and psychosis, suicide, and car crashes


That's a big assumption

Doubt cast on cannabis, schizophrenia link
http://www.cbc.ca...nia.html
NonRational
2.2 / 5 (5) Sep 29, 2009
It's disheartening to see how quickly people are to dismiss this report. I smoke pot. But I know firsthand the psychotic effects that people can suffer as a result of "normal" intake of THC. I lived and worked at a mental illness recovery center for 10 months, and met a great many people who developed psychosis after pot use. They freely admitted believing that it was their use of pot that caused their illness. Most of these people were no different than the majority of pot smokers I have known.

So, be careful before throwing out this study. Some people can seriously suffer from pot.
Thnder
5 / 5 (7) Sep 29, 2009
Correlation does not equal causation.
Shark attacks can be correlated with Ice Cream Consumption…
Maybe you can correlate THC/cannabis usage to a psychosis, but you can not prove it is the cause by mere correlation.
morilinde
3.3 / 5 (4) Sep 29, 2009
It's disheartening to see how quickly people are to dismiss this report. I smoke pot. But I know firsthand the psychotic effects that people can suffer as a result of "normal" intake of THC. I lived and worked at a mental illness recovery center for 10 months, and met a great many people who developed psychosis after pot use. They freely admitted believing that it was their use of pot that caused their illness. Most of these people were no different than the majority of pot smokers I have known.

So, be careful before throwing out this study. Some people can seriously suffer from pot.


Thinking about things from new perspectives scares people and can shake their basic belief systems (which can make some people freak out). This means the drug is useful and people are just afraid of having their happy spoon fed beliefs dashed through logical considerations (which are stimulated by cannabis usage).
twango
4.3 / 5 (4) Sep 29, 2009
Oh please. "Reefer madness" redux? How about studying how much violence alcohol causes?

Some gang with nothing better to do - and needing the grant - might "study" such a concept. After all, "psychosis", like "terror", is such a malleable word. But ... what's that got to do with physics? Science? Or news?

Meanwhile, in the latest edition of "Witch Doctor Quarterly" ...
ormondotvos
4.5 / 5 (6) Sep 29, 2009
If I were prepsychotic, I might very well self-medicate with a variety of potions. And I suspect if I tried pot first, I might not become a drunk...
psychdoc
5 / 5 (4) Sep 30, 2009
From the report:

"cannabis was not a major contributor to disease burden in Australia, accounting for 0.2% of all disease burden, which amounted to 10% of the total burden attributable to all illicit drugs."

A total disease burden of .2% and 10% of the burden for all illicit drugs. However, marijuana is the most used illicit drug in Australia (34% lifetime use and 11% use this year). This would mean then that a little over 1/2 of 1% of those who use marijuana will likely experience (or cause others to experience) health problems related to one of three categories: psychosis, suicides or car crashes. This amounts to a little over 42,000 people out of 21+million. Which is the more likely health impact on these 42,000: psychosis, suicide, or a car crash? The baseline prevalence rate for schizophrenia (only one type of psychotic disorder) in the population is already 3/4 of 1%. The association could be due in part to an availability heuristic.
VOR
Sep 30, 2009
This comment has been removed by a moderator.
moebiex
5 / 5 (2) Oct 02, 2009
I interpret this as saying we should get some objective measures on the impact so we do not have to be held hostage by opinion. That makes a lot of sense to me and I suspect this sort of measure has more potential to undercut prohibition arguments than those for reasonable use and legalization. It might also eventually allow identification of genetic markers associated with risks from use and thereby provide good objective and tailored medical advice to those who really should not play around with the stuff. I don't see a problem with that.
jerryd
5 / 5 (1) Oct 03, 2009
It's disheartening to see how quickly people are to dismiss this report. I smoke pot. But I know firsthand the psychotic effects that people can suffer as a result of "normal" intake of THC. I lived and worked at a mental illness recovery center for 10 months, and met a great many people who developed psychosis after pot use. They freely admitted believing that it was their use of pot that caused their illness. Most of these people were no different than the majority of pot smokers I have known.
So, be careful before throwing out this study. Some people can seriously suffer from pot.


By your reasoning mental illness would be caused by drinking milk!! Maybe they would rather blame their illness on a drug rather than themselves. If you had been any good at helping mentally ill you might have known about that.

Drug abuse is a symptom, rarely a cause of illness.
zevkirsh
5 / 5 (2) Oct 03, 2009
In america, the war on drugs, and the resulting pstd and chronic stress that result from the enforcement actions (and subsequent court and incarceration actions)of the DEA , police, and other authorities, on a mostly, passive calm and relaxed pot smoking and pot distributing populace causes far more psychosis ( not too mention rival drug gangs in-fighting) than does the actual smoking of pot.

if you legalized pot, there'd be more smokers and more pot psychosis but so much less war on drugs psychosis that it would be more offset.