Just say “No causal link”

Reefer not wholly to blame for madness

On Monday, the British Government announced the reclassification of cannabis from a “Class C” to a “Class B” controlled substance, leading to stiffer penalties for those found guilty of possession.  But is this reclassification based on scientific evidence, or is it, as the Liberal Democrats claim, mere posturing?

Home Secretary “Wacky” Jacqui Smith’s decision to reclassify cannabis represents a significant change in government policy, reversing a previous downgrade in 2003, and explicitly contravenes the recent recommendations of the Advisory Council on the Misuse of Drugs, who concluded the drug should remain Class C.

Denouncing the decision, Liberal Democrat MEP Chris Davies, doubtless clutching a well-thumbed copy of On Liberty by John Stuart Mill, told the BBC: “The principle of a free society is that people should be able to do whatever they like as long as they cause no harm to other people.”

Home Office Minster Alun Campbell, on the other hand, laid to rest any lingering doubts that his government considers its populace capable of making informed choices about their lifestyle, saying: “We are reclassifying cannabis to protect the public and future generations.”

But let’s lay politics aside and assume, for the sake of argument, that the British really are a bunch of hopeless children in need of constant protection from their own malign influence. After all, the Home Secretary fears continuing “uncertainty” over the mental health ramifications of tucking into an eighth of skunk, while the popular press remains crammed with first-person human interest stories in which “cannabis destroyed my life“.

So let’s act like grown-ups and face the music: is there any causal link between cannabis use and the onset of mental ill health?

Despite the presence of two million tokers roaming the streets of Britain, a recent meaure of the incidence of psychosis in Britain found 83 schizophrenic diagnoses per 100,000 individuals aged 20-24. which is a low return by any meaure.  The question must be: are a significant number of these incidences attributable to cannabis consumption?

Not if a recent Danish study is anything to go by.

“Cannabis-induced psychosis” is a diagnosis not uncommonly given to pot-heads who become strangers to reason. But it is not entirely uncontroversial, either. The devil is in the “induction”, if you will.

Addressing this very question, Mikel Arendt of Aarhus University Hospital studied the records of 2.25 million Danes born between 1955 and 1990, among whom “609 individuals received treatment for cannabis-induced psychosis and 6476 received treatment of a schizophrenia spectrum disorder”.

Previous studies unconcerned with cannabis have found a “predisposition to schizophrenia” among individuals having a “first degree relative” with the condition, which is to say: if a parent or sibling suffers from schizophrenia, you are more likely to develop it yourself.

Pertinent to the present argument, however, is the finding that those diagnosed with cannabis-induced schizophrenia are just as likely to be “predisposed” in this fashion as those who are diagnosed with schizophrenia associated with other factors.

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.

Arendt told Reuters, in somewhat simpler terms: “These people would have developed schizophrenia whether or not they used cannabis.”

Sometimes, especially when I read about our government’s legislative decisions, I wonder whether the Enlightenment ever happened.

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