Something I've been saying for sometime now...

[Gob]

Many studies have linked marijuana use with early onset of psychosis. The question is, does smoking marijuana cause earlier psychosis? A new review of 83 studies involving more than 22,000 participants seeks an answer.

The meta-analysis found that people who smoked marijuana developed psychotic disorders an average 2.7 years earlier than people who did not use cannabis. But the review also found that people who used any illegal drug suffered psychosis two years earlier than non-users, not a large difference.

While alcohol use was not associated with early onset, the studies reviewed could not rule out the influence of cigarette smoking, which is a common habit of people with psychotic disorders and those who smoke marijuana. In many of the countries from which the data was gathered, in fact, cannabis is typically smoked mixed with tobacco. The researchers argue that cigarette smoking—unlike marijuana— does not worsen hallucinations or paranoia in patients with schizophrenia, so they believe that tobacco does not account for earlier onset.

Led by Mathew Large of the University of New South Wales in Australia, the authors of the new research review also focused on other factors that may have contributed to the association between pot smoking and early psychosis in previous studies. For instance, it's known that men are both more likely to take drugs and to develop psychosis at an earlier age than women, and the preponderance of men in past studies might have contributed to the connections found. It's also known that young people, including those who have schizophrenia, are more likely to smoke pot than older folks, so previous studies that put upper age limits on their participants could have overstated the marijuana-psychosis link.

But based on the meta-analysis, researchers found that the link persisted independently of these factors. In the paper, published in the Archives of General Psychiatry, they conclude that their results "provide evidence for a relationship between cannabis use and earlier onset of psychotic illness and they support the hypothesis that cannabis use plays a causal role in the development of psychosis in some patients."

The research adds to the evidence that marijuana smoking may be dangerous for people with a family history of psychosis. TIME recently reported on a study that found that among 190 patients with schizophrenia, 121 of whom had used marijuana, cannabis appeared to affect the age of psychosis onset in a subgroup of 44 patients. The affected patients either had their first symptoms within a month of smoking pot for the first time, or experienced a severe worsening of psychotic symptoms each time they smoked.

The cannabis-sensitive patients not only developed psychosis nearly three years earlier than patients who were unaffected by the drug, but they also had three times the number of close relatives with psychotic disorders.

In the new review, researchers also cite studies linking a particular gene to sensitivity to cannabis, which could help explain why most marijuana smokers don't have a higher risk of schizophrenia, and why even many people with schizophrenia do not have earlier onset connected with cannabis use.

Still, none of the data linking marijuana use and psychosis can prove causality or sufficiently explain why rates of schizophrenia have remained stable or even declined since the 1950s, while marijuana use has increased exponentially. Unlike rates of cigarette smoking and lung cancer, which rise in tandem, marijuana smoking rates in the population do not correlate with higher rates of schizophrenia.

Either way, it's now clear that if you have any close relatives with schizophrenia or other psychotic disorders, it's better to steer clear of marijuana, particularly during adolescence when the brain is undergoing significant development.



Read more: http://healthland.time.com/2011/02/07/m ... z1DLOOUfpp

[Andrew D]

It's all in what one chooses to emphasize:

Still, none of the data linking marijuana use and psychosis can prove causality or sufficiently explain why rates of schizophrenia have remained stable or even declined since the 1950s, while marijuana use has increased exponentially. Unlike rates of cigarette smoking and lung cancer, which rise in tandem, marijuana smoking rates in the population do not correlate with higher rates of schizophrenia.

Marijuana use has gone way way up while schizophrenia incidence has not. In the face of that, claiming that marijuana causes, even in part, schizophrenia is a very tough row to hoe.

What a difference a font size makes ....

[Gob]

Marijuana use has gone way way up while schizophrenia incidence has not. In the face of that, claiming that marijuana causes, even in part, schizophrenia is a very tough row to hoe.

Which is probably why no one has claimed that.

What's not deniable is that cannabis has an effect on a percentage of the population's mental health prognosis though.

[oldr_n_wsr]

I would bet any mind altering drug, from cannibis to alcohol to probably coffee play a role in our collective phsocisisies. (is that a word??)
Seems we all will end up with some problem.

[Crackpot]

I wish I could get some coca tea here.

[BoSoxGal]

psychoses

[rubato]

Sounds more like correlation than causation. Drug users are probably less able to hide the early symptoms of psychosis and thus diagnosed earlier in the course of the disease.


And the OPPOSITE trends in marijuana use and schizophrenia is very powerful proof that there is no causation.


yrs,
rubato

[rubato]

"...
What's not deniable is that cannabis has an effect on a percentage of the population's mental health prognosis though.

Actually that is deniable. Earlier diagnosis is not a significant change in prognosis when there are few effective treatments or cures. Almost none.

yrs,
rubato

[Gob]

The scary thing of course is that with an earlier onset exaacerbated by cannabis use the worse the prognosis for the sufferer.

[loCAtek]

It's all in what one chooses to emphasize:

Still, none of the data linking marijuana use and psychosis can prove causality or sufficiently explain why rates of schizophrenia have remained stable or even declined since the 1950s, while marijuana use has increased exponentially. Unlike rates of cigarette smoking and lung cancer, which rise in tandem, marijuana smoking rates in the population do not correlate with higher rates of schizophrenia.

Marijuana use has gone way way up while schizophrenia incidence has not. In the face of that, claiming that marijuana causes, even in part, schizophrenia is a very tough row to hoe.

What a difference a font size makes ....

Skewing the data; psychosis generally predates schizophrenia.

Stats show psychosis is up, but that prediagnosis PREVENTS it leading to schizophrenia. Early treatment is dropping the schizophrenic population.

[rubato]

I have seen no evidence that early diagnosis has any effect on developing schizophrenia.

yrs,
rubato

[loCAtek]

Schizophrenia can remain latent longer, if factors triggering psychotic episodes are kept to a minimum; such as drug use.

[Gob]

Some interesting points from the study, (I've got a PDF of it if anyone is interested.)

"Meta-analysis of age at onset of psychosis revealed that the age at onset was 2.70 years earlier among samples of cannabis users ….and was 2.00 years earlier in samples with unspecified substance use compared with non-substance-using controls."

"this study lends weight to the view that cannabis use precipitates schizophrenia and other psychotic disorders, perhaps by an interaction between genetic and environmental factors…."

"Our findings do not support the view that people with a propensity to develop psychosis at a young age are simply more likely to use all substances, because alcohol use was not associated with a younger age at onset."

"The results of this study provide strong evidence that reducing cannabis use could delay or even prevent some cases of psychosis."

"Reducing the use of cannabis could be one of the few ways of altering the outcome of the illness because earlier onset of schizophrenia is associated with a worse prognosis and because other factors associated with age at onset, such as family history and sex, cannot be changed."

"….even if the onset of psychosis were inevitable, an extra 2 or 3 years of psychosis-free functioning could allow many patients to achieve the important developmental milestones of late adolescence and early adulthood that could lower the long-term disability arising from psychotic disorders."

"The results of this study confirm the need for a renewed public health warning about the potential for cannabis use to bring on psychotic illness."

[Big RR]

Or does a propensity to psychosis lead to a higher likelihood of the use of cannabis and/or other drugs?

[Gob]

If so, then alcohol would re the first port of call:

"Our findings do not support the view that people with a propensity to develop psychosis at a young age are simply more likely to use all substances, because alcohol use was not associated with a younger age at onset."

[Gob]

and still the reports pile up.....

Cannabis use 'raises psychosis risk' - study

2 March 2011 Last updated at 01:23 GMT

The participants in the study were aged between 14 and 24

Using cannabis as a teenager or young adult increases the risk of psychosis, a report suggests.

The study published in the British Medical Journal involved tracking 1,900 people over a period of 10 years.

Although the link between cannabis and psychosis is well-established, it had been unclear whether cannabis triggers the disorder.

This research strongly suggests that cannabis use comes first, rather than people taking it for their symptoms.

The research was led by Professor Jim van Os from Maastricht University in the Netherlands, and included researchers from the Netherlands, Germany, Switzerland and the UK.

They excluded anyone who reported cannabis use or pre-existing psychotic symptoms at the start of the study, which took place in Germany.

The participants in the study, aged between 14 and 24, were assessed for cannabis use and psychotic symptoms at three points over a ten-year period.

It found that cannabis use "significantly" increased the risk of psychotic symptoms, even when other factors such as socio-economic status, use of different drugs and other psychiatric conditions were taken into account.

Three years ago the Labour government restored cannabis to Class B - against the advice of its own drug advisers who said cannabis played only a "modest" role in the development of psychotic illnesses.

http://www.bbc.co.uk/news/uk-12616543

BMJ article

[Andrew D]

What percentage of people who use cannabis develop psychosis?

[Gob]

I'll try and find you a good clear figure Andrew.

http://aje.oxfordjournals.org/content/156/4/319.full

In conclusion, this prospective study confirms previous suggestions that cannabis use is an independent risk factor for the emergence of psychosis in psychosis-free persons and that those with an established vulnerability to psychotic disorder are particularly sensitive to its effects, resulting in a poor outcome. These findings have public health implications. If a causal relation between cannabis use and psychosis outcome is assumed, the population attributable fraction—that is, the maximum proportion of psychosis outcomes attributable to cannabis use in psychosis-free subjects—is higher than 50 percent. Although this high percentage can be misleading because it also includes the effects of all other causal risk factors that interact with cannabis, there is nevertheless cause for concern given the widespread use of cannabis by adolescents and young adults (39–41). The percentage of cases that may be prevented by suppressing exposure to this risk factor may not be negligible.

[Gob]

John McGrath of the Queensland Brain Institute in Australia studied more than 3,801 men and women born between 1981 and 1984 and followed them up after 21 years to ask about their cannabis use and assessed them for psychotic episodes. Around 18 percent reported using cannabis for three or fewer years, 16 percent for four to five years and 14 percent for six or more years.

"Compared with those who had never used cannabis, young adults who had six or more years since first use of cannabis were twice as likely to develop a non-affective psychosis (such as schizophrenia)," McGrath wrote in a study published in the Archives of General Psychiatry journal.

They were also four times as likely to have high scores in clinical tests of delusion, he wrote, and a so-called "dose-response" relationship showed that the longer the duration since first cannabis use, the higher the risk of psychosis-related symptoms.

A study by British scientists last year suggested that people who smoke skunk, a potent form of cannabis, are almost seven times more likely to develop psychotic illnesses such as schizophrenia than those who smoke "hash" or cannabis resin.

http://www.reuters.com/article/2010/03/ ... LW20100301

[Andrew D]

I do not see an answer to my question in there. (Not that I do not see anything potentially useful, just not an answer to my question.)

The statement "If a causal relation between cannabis use and psychosis outcome is assumed" immediately causes me to wonder (a) why should we make that assumption? and (b) what would the figures look like without that assumption?

John McGrath (and, I assume, those assisting him in the study) both "ask[ed the subjects] about their cannabis use and assessed them for psychotic episodes." Should not such a study have been double-blind? That is, should not the people assessing the subjects for psychotic episodes have been walled off from the information about the subjects' cannabis use?

Anyway, the fundamental public-policy question, it seems to me, ought to be whether cannabis use poses a policy-significant risk of psychosis. If, for example, the numbers show that only a tiny fraction of cannabis users develop psychoses (even if cannabis use makes it substantially more likely that one will become part of the minuscule fraction of cannabis users who develop psychoses), then the risk that a cannabis user will develop psychosis ought to be regarded, from a public-policy perspective, as negligible.