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Abstract
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Cannabis is a substance that is shrouded in myth, paradox, and controversy. On the one hand, a host of literature indicates detrimental effects on areas such as mental health (eg, increased risk of schizophrenia and poorer prognosis among patients with psychiatric disorders who also use cannabis), risk of addiction, and psychosocial functioning.1, 2, 3, 4 On the other hand, there has been an increase in public perception of cannabis as relatively harmless, as well as international movements to legalise cannabis for medicinal or recreational purposes.5 Of course, this does not necessarily constitute a paradox—benzodiazepines and opioids are also used both recreationally and medicinally, and with both positive (eg, reduction of pain or anxiety) and negative (eg, addiction or death) effects.
However, the controversy appears to run deeper in the case of cannabis, probably because of the counterculture that has existed around the substance for the past 50 years. Cannabis is increasingly seen as harmless, perhaps because it is a natural product.5 Observed negative effects on mental health are, in this viewpoint, seen as stemming solely from self-medication. This controversy has also existed in the scientific community. Within a rather short time period, two systematic reviews were published in The Lancet.1, 6 The first concluded that the associations between cannabis and psychosis were most likely explained by non-causal or selection mechanisms.6 The second concluded that, although causality between cannabis and psychosis was difficult to establish, there was ample reason to be cautious because evidence was pointing in this direction.1 Since then, much research has been published, and there appears to be a growing scientific consensus that cannabis does have a causal role in the development of psychosis. Indeed, the association appears to be bidirectional, so both hypotheses are probably correct.7, 8 In some people, cannabis leads to incident psychosis, whereas in other people, psychosis leads to incident cannabis use.
This growing scientific consensus is not reflected in the mainstream public discourses, which have a major effect on the political agenda to decriminalise or legalise cannabis. It also appears that, in many places (eg, several US states), the first thing to be legalised is medicinal cannabis followed by increasing decriminalisation and sometimes complete legalisation of cannabis. It is thus of utmost importance that the public and politicians are informed of the most up-to-date evidence on cannabis ...
Language: en |