If you use cannabis heavily for a long period, you are likely to suffer cognitive impairments and changes in brain structure that resemble those associated with schizophrenia. Some of these impairments are reversible, others may not be. Such was the bad news shared yesterday by Australian researcher Nadia Solowij at the 2013 International Drug Policy Symposium Through the maze: Cannabis and Health.
One of the ironies of this kind of research is that it has become possible essentially because there is now a cohort of people who have smoked marijuana daily, or nearly so, for two or three decades. The effects are dose-dependent, but what actually constitutes "heavy use"? Is it simply near-daily use? No: it seems a bit bit more complicated than that.
At one point, Nadia referred to her subjects smoking around seven joints a day. I know a few people who smoke pot several days a week, but I don't know any anyone who consumes marijuana at that degree. I interviewed Nadia afterwards and she confirmed that figure -- and said that some of her subjects consumed cannabis at the level of a heavy tobacco smoker: 20-25 joints a day.
Her group self-selected for the study by answering a newspaper ad. Some seem to have come forward precisely because they did have concerns about impairments in attention, memory, learning or planning, but all, she said, were living "functional lives". The group even included company CEOs. It would be interesting to note the effects of comparably heavy consumption of other psychoactive drugs, including alcohol.
But the fact is, cannabis causes harm. According to Professor David Fergusson, founder and director of the Christchurch Health and Development Study, using cannabis raises the relative risk of a range of negative outcomes, from having a car accident to psychotic symptoms.
Here is where we remind ourselves of the difference between relative risk and absolute risk -- the very large majority of people who use cannabis suffer no meaningful harm. And of the apparently perverse findings of this kind of research -- Professor Fergusson had found no correlation between use of alcohol and committing crime. The use of alcohol is so universal that the effects tend to disappear within the cohort. If we did it the other way -- started with recorded crimes and worked back to look at correlations -- we would get quite different results with respect to alcohol.
Some in the cannabis law reform community haven't been happy with this "negative" focus at the symposium, but this is a conference with "Health" in its title, and this is health research. And all of the research points us to one key issue: age of onset. The outcomes for people who begin using marijuana before the ages of 18 or 20 are predictably and significantly worse than for those who start later. If you have kids, "just say no" probably isn't going to work. Dropping a little "science says wait" message might be more effective.
Also: not a single one of the experts who spoke today gave advice in line with actual trends in cannabis enforcement: which are, as JustSpeak's Sacha Norrie pointed out, increasingly punitive (especially for Maori, who are prosecuted at a much higher rate than non-Maori). The rate of marijuana apprehensions that lead to prosecution (as opposed to warnings and the like) has doubled in the past 20 years. Professor Fergusson still favoured cannabis remaining illegal but believed the sole penalty for possession should be confiscation of the goods.
Even the staunch American prohibitionist Kevin Sabet agreed when I interviewed him yesterday that it was essential to curb the harms of criminalisation but, as ever, was vague about how we'd do that. In my view, the evidence is that the criminal status of cannabis does not greatly deter use (most people in New Zealand who smoke pot stop, and very few of them stop because of the law) but it does make is more difficult to seek help for problematic use. We really are doing it wrong.
There's one more really key point here, which has emerged in quite different ways at the symposium. Which is that a key factor in resilience to harms from cannabis and other drugs lies not just in the individual, but in the community around the individual. Professor Steve Allsop of Australia's Nation Drug Research Institute said this to me yesterday -- that key factors in curbing drug harm were social, "even spiritual". Having a reason to get up in the morning makes a big, big difference. And Lani Hunt spoke from the stage as someone who had lived that. The former rough-sleeping kid experienced his turnaround as he walked on to the marae at Parihaka, via a sensation that a kuia interpreted for him as the feeling of connecting with his tipuna.
There are good people working on that front in New Zealand, and they struggle with the level of funding for their work, and even (as Lani did) lose that funding altogether. We really need to think about our priorities.
NB: The six video interviews I conducted yesterday at the symposium should be online by tomorrow.