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  1. chillinwill
    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, high blood pressure, 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 schizophrenia. 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.''

    This work was given funding support from the Australian Government Department of Health and Ageing. LD is the recipient of an Australian National Health and Medical Research Council (NHMRC) Senior Research Fellowship.

    Journal reference:

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

    September 29, 2009
    Science Daily
    http://www.sciencedaily.com/releases/2009/09/090929012259.htm

Comments

  1. corvardus
    For the document I have uploaded it: Burden of disease andinjury in Australia 2003
  2. Nature Boy
    Wow! 0.2% is remarkably low. As something of a cannabis-induced schizophrenia skeptic, even I find that number to be way below what was expected.
  3. MrG
    I have a theory, one I have some pretty solid anecdotal evidence for.

    Psychotic illness isn't due to cannabis. It is more likely that, as we already know, dysfunctional childhood environments damage both the psychology and physiology of the developing brain. As adults, young or old, begin using cannabis recreationally, it triggers recall of distressing memories, not always visual, for they can be emotional memory and difficult for the user to understand and relate to why they feel what they are feeling and so it gets associated with "the now" instead of their past, with this in turn resulting in a state of anxiety which can affect one's sleep cycle, to the degree that paranoid schizophrenia can develop, incorrectly attached to something "in the now" (conspiracies etc.) which can then become a self-serving prophecy as, with the user's behaviour begining to become more erratic, people close to them start to show concern which, unfortunately can be interpretted by the sufferer as being part of the conspiracy.

    Delusional states can be rooted in strong, inappropriate, emotions that will reinforce the delusion, thereby excacerbating the situation. These can range from murderous or violent acts as a result of fear or rage, through to rapturous, yet still as equally delusional, spiritual experiences.

    Both extremes of delusion are as irrational as each other, but society doesn't have much of a problem with people who claim to have seen god, angels, visitations from the dead, etc. You're only crazy if you smoked dope and did something that falls outside the accepted behavioural boundaries of your society.
  4. Amnesia
    SWIM wonders if this research has taken family pedigree in to account as well as cannabis use, as schizophrenia has a heritability factor estimated at up to 80%, thus showing it to have some firm genetic basis.

    In a study published in the journal Nature this year, over 50,000 patients and control subjects were examined. Amongst other things, it noted that there were a disproportionately large number of schizophrenic patients born in either winter or spring to mothers who were pregnant during the influenza season. It demonstrated that the children of mothers who contracted influenza whilst pregnant have a higher risk of developing the illness, concluding that in vitro mutations of the chromosomes are an important risk factor for the development of schizophrenia.

    Also, schizophrenia - and other illnesses that involve psychosis - usually starts to manifest in adolescence, which is often when people begin to experiment with drugs. Linking cannabis use to schizophrenia/psychosis seems (at least to SWIM) akin to linking the MMRI jab to autism – just because they tend to occur around the same time as one another doesn’t mean that one causes the other.

    SWIM will wait for a lot more unbiased scientific evidence before she believes cannabis is a fundamental factor in causing severe mental health problems.
  5. MrG
    I'd question many of the assumptions made regarding genetic disposition to mental illness. Exactly how would a control group be found in society? How can research projects account for general dysfunction within a person's developing years if the individual has managed to overcome many of the crippling symptoms and that these symptoms (Borderline Personality Disorder for example) only manifest themselves under stress and often just get ascribed to simply being "how that person is".

    There's a damn good reason why those born to parents with known mental illness will grow to develop the same condition, because the resultant dysfunctional environment will create the same damage within them as did their ill parent. Plus, in order for a parent to be a known sufferer of the condition, their condition needs to be manifesting itself severely enough that the "system" has been able to recognise and label them as such.

    What about all the other parents who, behind closed doors, were violent, inappropriate or inadequate but who's children grew up believing that it was "the norm" and simply managed to survive it?

    Where the hell is this, supposed, "control" group found exactly?
  6. Amnesia
    The study cited examined schizophrenia and bipolar disorder so SWIM can not comment on borderline personality disorder. However, personality disorders are believed (at the moment) to stem primarily from life experience.

    Post mortem examinations, PET scans and nMRI scans can show minute (and sometimes large) changes in the structure of the brain in people with schizophrenia and bipolar disorder. Scans can also display significant changes in the levels of neurotransmitters in the brains of those with severe mental health problems.

    The genetic predisposition is demonstrated by adoption studies (when the child of a person with severe mental health problems is raised by psychologically 'normal' parents), by family pedigrees and by twin studies.
    There are many children raised in abusive circumstances that do not go on to develop schizophrenia or manic depression, so the idea that nurture is the sole cause can not be true. Consider the populations of deprived, poor or war torn countries - if life stresses were the only factor in the development of these two conditions then the prevalence would be higher there, and in countries that have recently developed.
    In fact, if environmental factors were the sole cause, given the current stress many people are facing due to the economic climate - job losses, home repossessions etc - the prevalence would be rising. The same thing happened in the 1980s too. However, for the last few decades the prevalence has remained the same; 1% of the population suffers from schizophrenia, 2% suffer from manic depression/bipolar disorder.

    Type 1 diabetes can lie dormant for many years then be triggered in later life by environmental circumstances, yet the genetic predisposition for this is not questioned. It is a useful analogy to schizophrenia and manic depression. Due to a genetic flaw a diabetic person can not control their insulin levels; in schizophrenia and manic depression, due to a genetic flaw, a person can not control their neurotransmitter levels.

    SWIM does however agree that a control group is a difficult thing to find for mental health problems. The idea of what is psychologically normal varies between societies; deviations from the cultural norm are considered ‘problems’ which need to be rectified. In this study the control group was comprised of people with no personal or family history of mental health problems.
  7. toluene
    SWIM works in mental health and has always been interested in this area. Bottom line - although the numbers of people smoking canabis in the UK has increased massively in the last 30 years, the number of diagnoses of schizophrenia have remained stable. However, there does seem to be some concerns about under 18's smoking large amounts of very strong weed. SWIM's understanding is that teenage brains are vulnerable because they are under going significant changes. The dangers are increased when smoking weed that has been bred to maximise THC content at the expense of some of the other cannabanoids, some of which may protect against psychosis.
  8. enquirewithin
    Good points. No one under 18 should be taking any drugs, but how do you stop them?
  9. MrG
    I keep hearing about schizophrenia and bipolar and all I know is that stress-induced sleep disturbance can induce schizophrenic type behaviour which is self-serving (triggering more stress and even worse sleep cycles) and that Bipolar Disorder is bandied about more and more, yet most patients' symptoms describe an ultra-rapid cycling state which actually fits the profile of Borderline Personality Disorder more than it does Bipolar.

    Toxic Stress is responsible for actual physiological alterations in the developing brain, often due to the constant "hyper-aroused" state the child is in as a result of the dysfunctional environment they are living in.

    BTW, please don't quote studies that have attempted to prove genetic disposition through analysis of adopted siblings. The adoption process throughout the years has proven to serve the interests of the adults involved rather than the child, so just because a child is raised by 'normal' parents, it doesn't make them good parents and it doesn't qualify that child as having been raised in a truly healthy, nurturing environment.

    "It's for your own good"
    "This'll hurt me more than it hurts you"
    "It never did me any harm"

    Three of the biggest lies we are indoctrinated to believe as children.
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