One of the most common refrains you hear when discussing the cannabis issue is that cannabis nowadays bears little resemblance to the cannabis that commentators and policymakers smoked back in their university days. Back then it was ‘grass’, ‘herb’ and ‘weed’ – all natural-sounding substances which made you giggly and mellow. Now much of it is ‘skunk’, a substance that is more potent and more dangerous. Skunk is a substance that is often mind-altering rather than merely mood-altering.
Skunk is an independent strain of cannabis with its origins dating back to the 1970s, although the term is now used more broadly to refer to much of the strong cannabis, which accounts for around 80% of the UK market. It’s in that context that I shall use the word throughout The Tide Effect: not as a substance different from ‘ordinary’ cannabis, but simply a much stronger version of it.
Cannabis contains many different compounds, but two of the major ones (and the most relevant when assessing the drug’s strength and effect on its users) are tetrahydrocannabinol (THC) and cannabidiol (CBD). THC helps the user get high, whereas CBD reduces feelings of anxiety.
What’s important is not just the amount of THC and/or CBD but also the balance between them. In the past 20-25 years the general trend amongst cannabis producers, especially those using hydroponic techniques, where plants are grown under strong artificial lights in nutrient-rich liquids rather than soil, has been to increase THC levels while selectively breeding out the more protective cannabinoids. Increased THC levels mean increased potency and increased prices per unit, so there is every incentive for dealers to pursue this path. The higher the ratio of THC to CBD, the greater some scientists believe the risks to the user, particularly concerning dependence, memory impairment and psychosis. 1
"The main reason skunk causes such disquiet is purported links with mental health problems"
The question is this: exactly how much stronger than its predecessor is modern-day skunk? The majority of sound scientific estimates seem to settle around a 15-18% THC concentration, around three times what it was in the mid-1990s. However, this can be exacerbated by the often almost total absence of CBD.
Skunk’s strength, and the speed of its effects, can catch inexperienced users out, leading to anxiety attacks, projectile vomiting, altered time perception, transient hallucinations and paranoia. More experienced users develop higher tolerance levels and also tend to autotitrate (adjust the amount they smoke to take account of higher strength joints).
But the main reason skunk causes such disquiet is purported links with mental health problems, particularly psychosis and schizophrenia. Professor Sir Robin Murray, Professor of Psychiatric Research at King’s College London, is one of the most vocal campaigners for official recognition of a causal link between cannabis use and mental health. According to Murray ‘If the risk of schizophrenia for the general population is about 1%,’ he says, ‘the evidence is that if you take ordinary cannabis it is 2%; if you smoke regularly you might push it up to 4%; and if you smoke skunk every day you push it up to 8%.’ 2 At the launch of a medical paper in 2015, he said ‘we could prevent almost one quarter of cases of psychosis if no-one smoked high potency cannabis. This could save young patients a lot of suffering and the NHS a lot of money.’ 3
The emphasis on ‘young patients’ is one shared by many scientists, who stress that a developing teenage brain is far less well-equipped to deal with the effects of skunk than a mature adult one. A 2012 New Zealand study found that people who smoked significant amounts of cannabis as teenagers showed a significant drop in their IQ levels compared both to non-consumers and to those who only began smoking after the age of 18. 4 And a 2009 report by Professor Stuart Reece of the University of Queensland found that ‘cannabis has now been implicated in the etiology of many major long-term psychiatric conditions including depression, anxiety, psychosis, bipolar disorder, and an amotivational state.’ 5
But this certainty is far from universal across the literature, and Murray’s assertions of causality between cannabis and schizophrenia have been repeatedly challenged. Former government advisor Professor David Nutt has written that ‘where people have looked, they haven’t found any evidence linking cannabis use in a population and schizophrenia… What we can say is that cannabis use is associated with an increased experience of psychotic disorders. That is quite a complicated thing to disentangle because, of course, the reason people take cannabis is that it produces a change in their mental state. These changes are a bit akin to being psychotic – they include distortions of perception, especially in visual and auditory perception, as well as in the way one thinks. So it can be quite hard to know whether, when you analyse the incidence of psychotic disorders with cannabis, you are simply looking at the acute effects of cannabis, as opposed to some consequence of cannabis use.
‘The analysis we came up with was that smokers of cannabis are about 2.6 times more likely to have a psychotic-like experience than non-smokers. To put that figure in proportion, you are 20 times more likely to get lung cancer if you smoke tobacco than if you don’t. The other paradox is that schizophrenia seems to be disappearing (from the general population), even though cannabis use has increased markedly in the last 30 years. So, even though skunk has been around now for 10 years, there has been no upswing in schizophrenia.’ 6
"Of course, whatever the links between cannabis and psychosis, the question for us is which policies reduce these harms"
More weightily, the New Zealand data on cannabis and IQ is consistent with confounding by socioeconomic status: those who smoked would have ended up with lower IQs anyway. 7 Social and genetic confounding affects the 2.6 relative risk ratio Nutt’s work returns as well: after accounting for those, standard estimates for England and Wales suggest you’d need to stop 2,800-4,700 heavy cannabis smokers from using the drug to prevent one case of schizophrenia. 8 You’d need to stop 1,360-2,480 to prevent a case of psychosis.
Of course, whatever the links between cannabis and psychosis, the question for us is which policies reduce these harms. Some evidence suggests that tighter control on cannabis, perversely, increases problems with psychosis. A 2014 study found that reclassifying cannabis as class C, in 2009, reduced admissions for psychosis, while returning it to class B increased them. 9
To assume that increased prohibition is the solution to the health risks of cannabis would be a mistake—precisely the opposite is true. Regulation would allow for both the THC and CBD content of cannabis products to be quantified, quality controlled and clearly communicated to consumers, provided alongside extensive and comprehensive health information which could then be built on by wider and deeper medical research. Skunk would still have harmful effects, as it always will do, but those effects would be both controlled and clearly outlined. At the moment, they are neither.
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