‘Cannabis Abuse’: Causation or Correlation?

A new study from Columbia University has attracted a great deal of press coverage in the past week. Published in the journal JAMA Psychiatry and authored by Carlos Blanco, MD, PhD, et al, you would be forgiven for thinking it was actually two separate studies, given the way in which it has been reported.

The reason for this is that the study looked at two different outcomes related to cannabis use, and made two distinct conclusions. In doing so, it highlighted brilliantly the biases and agendas of the news outlets who covered it.

On the one hand, there were the scare stories. These focussed on the finding of the study that is indeed cause for some concern – that cannabis users are more likely to abuse other substances, most notably alcohol, in later life. Naturally enough, many have been quick to conclude that since the statistics don’t lie, it must be the case that cannabis causes alcoholism.

It’s an example of a problem that has plagued research (or rather, interpretation of research) into cannabis for decades – the problem of causation vs. correlation.

The simplest way of interpreting the results of the study is to presume causation, but a more nuanced and thoughtful analysis provides serious food for thought. To do this means taking a look at the wider issue of addiction.

It is well established that as much as 90% of all drug use is non-problematic, meaning that it is not classed as ‘abuse’, and does not cause any real harm to the user. It is also well established that if someone is prone to an addiction of one kind, they are more likely to become addicted to, and to abuse, something else. In this context it is hardly surprising to hear that there are a certain number of cannabis users who will develop an addiction to alcohol, because we already know that there are a certain number of cannabis users who develop an addiction to cannabis.

Which brings us on to the other point about addiction. Many scientists and so-called experts will tell you that addiction is a ‘brain disease’, but this is wrong. It’s far better to view addiction as a symptom of a far wider problem.

Consider this: If you’ve suffered childhood trauma, you’re 4600% more likely to become an injecting drug user than if you haven’t. What this tells us is that addiction isn’t about the drug, it’s about the individual. Most addicts are using drugs to protect themselves from the pain of a childhood trauma, and treating them as ‘diseased’ instead of looking at, and treating, the underlying causes of addiction which pervade the whole of society, is treating the symptom rather than the cause. It’s marginally better than locking them up, but it still places the blame at the feet of the drugs themselves, and suggests that getting rid of drugs would get rid of the problem.

So despite much hand-wringing at the prospect of legalised cannabis leading to a surge in alcoholism, there is no need to panic. The statistics may not lie, but they don’t tell the whole story of addiction.

The second finding of the study, which was reported on more enthusiastically by supporters of reform and, bizarrely, the Daily Mail, was that contrary to popular belief, cannabis use does not increase your chances of mental health problems in later life.

There’s not much to say on this issue that hasn’t already been said, other than that those who reported it without mentioning the apparently negative findings of the study, are just as guilty of cherry picking as those who only mentioned the negatives. Or at least almost as bad, since those who led with ‘cannabis causes alcoholism’ failed to point out the apparent contradiction in reporting ‘proof’ of a causal link between cannabis use and what they consider a ‘brain disease’, and the part of the study which concluded that cannabis use doesn’t lead to mental ill-health.