Chronic Pain — 15 January 2013

file0001608617467By Richard Lenti

With the growing use of medical marijuana to treat chronic pain and other health problems, the debate over the medical effects of the drug on the human mind continue to make their way through the medical community.

The latest salvo comes from researchers in Australia and England.  At the center of the debate is the possible relationship between marijuana (cannabis) and mental illnesses such as schizophrenia.

In a pair of articles published in F1000 Medicine Reports, the authors were given the unique opportunity to read the opposing side’s drafts and consider their arguments when structuring their own article.

In his article “Cannabis and psychosis: what causes what?” David Castle of the University of Melbourne argues that a clear link exists between cannabis use and an increased risk of psychotic symptoms.

“There is little doubt that ingestion of the plant Cannabis sativa can cause positive psychotic-like symptoms.” Castle writes.  “A rather more contentious issue is whether cannabis can actually cause schizophrenia. This, of course, is very difficult to determine definitively.”

“It is clear that cannabis and related compounds can cause acute transient impairments in memory, attention, and executive function. But whether exposure to cannabinoids is associated with persistent cognitive deficits is not as clear.”

Castle cites one study that indicated people with schizophrenia had a lifetime rate of cannabis exposure of 97 percent – meaning almost all of them have tried the drug.  Yet, he also notes that most people who use cannabis do not develop schizophrenia, and that many people diagnosed with schizophrenia have never used cannabis.

“Therefore, it is likely that cannabis exposure is a ‘component cause’ that interacts with other factors to ‘cause’ schizophrenia or other psychotic disorders, but is neither necessary nor sufficient to do so alone,” Castle wrote.

However, the authors of the accompanying article are not as convinced that the prevailing scientific evidence proves a relationship exists between pot use and schizophrenia.

“Schizophrenia is a serious illness associated with substantial loss of quality of life, social and economic problems, co-morbidity and premature mortality,” they write, “and the need to improve primary prevention is paramount.”

But for Suzanne Gage, Stan Zammit and Matt Hickman of the Universities of Bristol and Cardiff, they say that from a scientific perspective, the extent to which the use of cannabis leads to an increased risk of schizophrenia remains uncertain.

In fact, they point out that some empirical comparisons of cannabis use and schizophrenia indicates just the opposite.

“There is evidence that cannabis use in many developed countries has increased greatly over the past 40 years. For example, in the United Kingdom, cannabis use has risen 10-20 fold since the 1970s,” they write. “However, recent data on new admissions for schizophrenia have shown no increase at all; indeed, there is a suggestion of a downward trend in diagnoses.”

They argue that more robust evidence is required to determine whether preventing cannabis use will have any substantial impact on preventing psychotic disorders in the population, or within specific high-risk subgroups.

Both sides agree that cannabis is a public health concern and that the public should be made fully aware of the risks associated with using the drug.

This particularly applies, Castle writes, to those who have a family history of schizophrenia or who have experienced psychosis-like symptoms, as they may be at greater risk.


About Author

Richard Lenti

Richard Lenti has worked as a news writer for the last 20 years at various television stations in Los Angeles. He is a Golden Mike winner and a graduate of California State University, Fresno. With roots in print journalism, Richard is excited to be “published” once again; having people read his work as opposed to having it read to them. As a freelance writer his work has appeared in the Easy Reader, L.A. Jazz Scene, Irrigation and Green Industry, and the KCAL 9 Online website.

(4) Readers Comments

  1. This article just simply wrote out in scientific terms the effects of marijuana while on consumption.. a marijuana consumer behaving psychotic?? Put it in the ‘street’ way, that’s called stoned on weed..
    Does marijuana cause schizophrenia?? Nope.. there may be a similar mild experience while on consumption.. but such effects aren’t permanent.. once consumption is stopped over time, the brain reverts to normal..
    On the contrary, since marijuana consumers are attuned to the effects while on consumption, they are more ready to adapt and handle any mental psychosis issues caused from depression, anxiety etc..
    I know, because I’ve been there..

  2. So sad to see these misguided “research” pieces, when there is so much good reason esearch that could be covered (Google “scholarly schizophrenia autoimmune” or the first two words with simple queries, like causes, latest research, etc.) Covering quality research would help people understand that what we lump together under a broad moniker may well be multiple psychosis producing illnesses that we haven’t sorted out.

    Or wait, maybe schizophrenia is caused by drinking cow’s milk or eating eggs. I mean, obviously there’s causation here….

  3. Malcolm you can keep pointing out the obvious but there are those who will continually try to inflate this issue and deliberately conduct studies with the clear intention of trying to prove what they want to believe, which makes them flawed from the onset, because of their agendas.

    I would also be curious to know who funded this study out of Australia? There is the national cannabis prevention and information centre in Australia who continually puts out negative clearly bias studies one after the other, they even put out a study trying to claim not too long ago that cannabis was twenty times more addictive than tobacco, a ridiculous claim under any circumstances but they did not even bother to account for tobacco use combined with the cannabis amongst users in Australia.

    As so called scientists who are suppose to professionally be impartial and be stringent in accounting for different variables I do not know how they can justify their existence in any form of research.

    It is clear to anyone who takes a close look at schizophrenia or even psychosis that there can be many factors, schizophrenia ironically is even linked to tobacco use by mothers during birth if I recall and more recently possibly infection during early childhood. There was also a recent paper put out linking all serious childhood mental illness to a flawed protein.

    I do not have a problem at with with the fact that cannabis can be a strong factor in the development of the mentioned mental health conditions but this desperate negative bias in some studies and the media gets us nowhere, changes nothing and does nothing for real science. Not to mention that cannabis is clearly here to stay, the quicker we accept that the quicker we can do some real science on the cannabis plant itself and helping prevent these illnesses. Ironically cannabinoids are anti-psychotic, it is THC that is the culprit in potentially triggering these symptoms/conditions, a little tweaking of the plant genetics and it is easy to put an addict on a type of cannabis that will prevent and potentially even help them; simple hey? Apparently it is easier to keep stamping feet.

  4. “Associated with” is not the same as “causation.”

    Schizophrenia affects approximately one percent of the population. That percentage has held steady since the disease was identified, while the percentage of people who have smoked marijuana has varied from about 5% to around 40% of the general population.

    Despite a massive increase in the number of Australians consuming the drug since the 1960s, Wayne Hall of the University of Queensland found no increase in the number of cases of schizophrenia in Australia. Mitch Earleywine of the University of Southern California similarly found the same with regard to the US population and Oxford’s Leslie Iversen found the same regard to the population in the UK. According to Dr. Alan Brown, a professor of psychiatry and epidemiology at Columbia University, “If anything, the studies seem to show a possible decline in schizophrenia from the ’40s and the ‘50s”.

    Kindly Google any of the following combinations:

    Nicotine and Schizophrenia
    Alcohol and Schizophrenia
    Chocolate and Schizophrenia
    Sugar and Schizophrenia
    Gluten and Schizophrenia

    So should we hand the market in any of the above substances to criminals (which is what prohibition effectively does) because its use is “associated” with a certain minute part of the population? Many bipolar patients misuse caffeine and tobacco in an effort to bring on a manic state, thus becoming a danger to themselves or others. Should tobacco and caffeine or whatever works for each individual be prohibited to boost ratings or rhetoric also? Where does it end?

    Persons with chronic mental illness die 25 years earlier than the general population does, and smoking is the major contributor to that premature mortality. This population consumes 44% of all cigarettes.

    Cigarette smoking rates in the American population are approximately 23%, whereas rates of smoking in clinical and population studies of individuals with neuropsychiatric disorders are typically two- to four-fold higher.

    Caffeine is most certainly linked with mental illness; psychosis even.
    Broderick, P. & Benjamin, A.B. (2004). Caffeine and psychiatric symptoms: a review. Journal of the Oklahoma State Medical Association, 97(12), 538-542.

    Hedges, D.W., Woon, F.L. & Hoopes S.P. (2009). Caffeine-induced psychosis. CNS Spectrums, 14(3),127-129.