Study clears cannabis of schizophrenia rap

By chillinwill · Nov 7, 2008 · ·
  1. chillinwill
    Regular readers will recall the confused mess that is this government’s cannabis policy. There has been a drop in cannabis consumption since it was downgraded from Class B to C, but nevertheless they want to put it back up to Class B again. Yes, we know all about the argument that what you ingest is entirely your business, it being your body and all that but morals are always trumped by politics.

    In the comments section to our last piece the general consensus was that the policy was driven either by a craven servility to the Murdoch press or, as a daring alternative, a bending to Daily Mail woo woo. The general consensus however was that it was Puritanism, that awful fear that someone, somewhere, might be enjoying themselves and that this situation cannot be allowed to continue. We’re arguing over whose Puritanism, not whether.

    There was one vaguely respectable argument that could be put forward on the prohibitionist’s side, that of cannabis induced schizophrenia. This has been increasing even as the general incidence of schizophrenia has been stable (or even falling, depending upon who you ask). That the rise was on the order of 500 people a year means it’s not a very important point, not when compared to 3 million regular tokers, but there are still those who will buy the argument that people should be stopped from harming themselves, even if the risks are very low.

    There is certainly a correlation, but we should still want to know about causation before we take any further action. For it is possible, and it is a view advanced by some (like myself last time), that those who are about to become schizophrenic dose themselves on cannabis as they are known to on alcohol and any other substance that comes to hand to still the voices. Or perhaps there’s a milder version, that cannabis induced psychosis isn’t in fact cannabis induced at all, but is simply coincidental: that it’s an early marker of schizophrenia rather than something brought on by cannabis itself.

    When we try to test this we also want to be very careful indeed about our sample groups. We really don’t want to be making the mistake that the World Health Organisation has been making with HIV testing in sub-Saharan Africa. Testing pregnant women to give you the incidence of a sexually transmitted disease in the general population really ain't all that clever: you’re testing the one group of the population where you have actual proof that they’ve been partaking in unprotected sex. It might be useful to get an idea of scale, but it's just not going to be all that accurate.

    Fortunately, all of this is just what some scientists have done (sadly, the full paper is not online for free access). We know that there is a genetic predisposition to schizophrenia (more accurately to three different conditions that we'll, for convenience sake, group together here). If we’re lucky we can also find a decent data set which we have indeed got, some 2.25 million Danes born between 1955 and 1990, and we know both their own treatments for either cannabis induced psychosis or for those varied schizophrenic type diseases. We can also track their familial relationships and see which of them did or didn’t suffer in these manners. Excellent, we can now try to test our correlation. Do people who have had cannabis induced psychotic episodes then go on to develop schizophrenia at a higher rate than their genetic predisposition (as evidenced by their familial incidence of schizophrenia) would lead us to believe they would?

    Well, looking at the 609 who had treatment for such pot induced freakouts and those 6,476 who were treated for the full blown nastiness, well, umm, no. Formally:

    In terms of estimated rate ratios, persons who develop cannabis-induced psychosis are as predisposed to schizophrenia spectrum disorder and other psychiatric disorders as those who develop schizophrenia spectrum disorder without a history of cannabis-induced psychosis.

    So at this point we can say that, no, that bad trip on some heavy shit does not lead on to schizophrenia. There’s no difference in incidence.

    But the paper’s authors go much further:

    Altogether, these findings, in addition to those of previous studies, indicate that cannabis-induced psychosis may not be a valid diagnosis but an early marker of schizophrenia.

    That is, that the very idea of that bad trip is itself wrong. The disease is already there, simply wrongly diagnosed as being cannabis induced. And finally we get:

    Rather, the degree of hereditary predisposition in individuals who receive treatment of cannabis-induced psychosis closely mirrors that in those who develop schizophrenia with no history of cannabis induced psychosis. The results agree with those of other studies that show that cannabis predominantly causes psychotic symptoms in those persons who are predisposed to develop psychosis or show signs of psychosis in the absence of cannabis use.

    This goes a great deal further than my or anyone else’s original supposition, that pot consumption might cause problems only for those who are already predisposed to mental health problems. If it were simply this then we could deal with legalised pot simply by placing warnings upon it, as we do with nuts and nut allergies (umm, 'nut' possibly isn’t le mot juste there). But this finding goes further. There seems to be no evidence that cannabis consumption increases the incidence of these mental diseases at all. Incidence is the same for those who have had the "cannabis induced" version as it is in the general population, adjusting for the risks we perceive from the incidence of such problems in their immediate families. That there’s actually nothing to do with cannabis at all, that it just so happens that some who are becoming schizophrenic, something which is often marked by short episodes before it fully takes grip, happen to have been puffing 'erb when such episodes hit.

    Thus there really is no logical leg for the government to stand upon in its reclassification of cannabis: there's not in fact one reason against the legalisation of the damn stuff and the increase in liberty and freedom that would result.

    So, anyone think this is going to make any difference? No, thought not myself. OK, back to basics then, could the Murdochists and the Mailites let us know who is really to blame for the idiocy which is current drugs policy?

    By Tim Worstall
    Posted in Policing, 6th November 2008 13:19 GMT
    The Register
    http://www.theregister.co.uk/2008/11/06/cannabis_psychosis_study/

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Comments

  1. Pondlife
    The source for this is "Familial Predisposition for Psychiatric Disorder / Comparison of Subjects Treated for Cannabis-Induced Psychosis and Schizophrenia" in the Archives of General Psychiatry http://archpsyc.ama-assn.org/cgi/content/short/65/11/1269

    The full text requires a subscription. The abstract reads:

    Familial Predisposition for Psychiatric Disorder

    Comparison of Subjects Treated for Cannabis-Induced Psychosis and Schizophrenia

    Mikkel Arendt, MScPsych, PhD; Preben B. Mortensen, DrMedSc; Raben Rosenberg, DrMedSc; Carsten B. Pedersen, MSc; Berit L. Waltoft, MSc

    Arch Gen Psychiatry. 2008;65(11):1269-1274.

    Context Cannabis-induced psychosis is considered a distinct clinical entity in the existing psychiatric diagnostic systems. However, the validity of the diagnosis is uncertain.

    Objectives To establish rate ratios of developing cannabis-induced psychosis associated with predisposition to psychosis and other psychiatric disorders in a first-degree relative and to compare them with the corresponding rate ratios for developing schizophrenia spectrum disorders.

    Design A population-based cohort was retrieved from the Danish Psychiatric Central Register and linked with the Danish Civil Registration System. History of treatment of psychiatric disorder in family members was used as an indicator of predisposition to psychiatric disorder. Rate ratios of cannabis-induced psychosis and schizophrenia associated with predisposition to psychiatric disorders were compared using competing risk analyses.

    Setting Nationwide population-based sample of all individuals born in Denmark between January 1,1955, and July 1, 1990 (N = 2 276 309).

    Patients During the 21.9 million person-years of follow-up between 1994 and 2005, 609 individuals received treatment of a cannabis-induced psychosis and 6476 received treatment of a schizophrenia spectrum disorder.

    Results In general, the rate ratios of developing cannabis-induced psychosis and schizophrenia spectrum disorder associated with predisposition to schizophrenia spectrum disorder, other psychoses, and other psychiatric disorders in first-degree relatives were of similar magnitude. However, children with a mother with schizophrenia were at a 5-fold increased risk of developing schizophrenia and a 2.5-fold increased risk of developing cannabis-induced psychosis. The risk of a schizophrenia spectrum disorder following a cannabis-induced psychosis and the timing of onset were unrelated to familial predisposition.

    Conclusions Predisposition to both psychiatric disorders in general and psychotic disorders specifically contributes equally to the risk of later treatment because of schizophrenia and cannabis-induced psychoses. Cannabis-induced psychosis could be an early sign of schizophrenia rather than a distinct clinical entity.

    Author Affiliations: Centre for Psychiatric Research, Aarhus University Hospital, Risskov (Drs Arendt and Rosenberg), and National Centre for Register-Based Research, University of Aarhus (Dr Mortensen and Messrs Pedersen and Waltoft), Aarhus, Denmark.
  2. Heretic.Ape.
    Good stuff. I'm having trouble getting onto my university network, but will upload the study to the archive later.
  3. Jatelka
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