Trade-offs in harm reduction – inevitable but (first) principled?

A commentary on Peter Gluckman’s blog Reducing harm: The challenge of difficult choices

Prof Richie Poulton, CNZM FRSNZ
Koi Tū Affiliate member

During the last four months, under a menacing COVID-19 cloud, politicians and health practitioners the world over have had to make important decisions under extreme pressure, about complex scenarios, in conditions of high uncertainty. Some decisions have been more straightforward than others. Some carried the ultimate consequences (e.g., early reports of Italian doctors deciding who will live or die using the simplest of criteria – the age of the patient). In the end it was the leader of each nation who carried the greatest burden, making strategic calls that profoundly affected their citizenry. From the outset it was apparent that science and evidence were crucial for optimising decision-making during this (first) acute phase of the COVID-19 crisis. The ‘truth’ of this has been sadly reinforced by the frightening reinvigoration of viral spread in nations where political leadership has shown contempt for scientific advice.

When it comes to the trade-offs required in the 2020 cannabis legalisation referendum, the balancing act involves far less angst. The core task (or at least it should be!) is to choose the best approach for minimising individual and societal harm. The stakes are not nearly as high as for COVID-19, but neither are they trivial. I am hopeful that evidence can play a helpful, guiding role in the referendum process as well.

So what does the evidence tell us about recreational cannabis use and its consequences? In a nutshell, it reveals that approximately 80% of middle-aged New Zealander’s have tried cannabis. The vast majority of users experienced no harm as a result. However, a non-trivial minority of the population (approximately 10%), especially those beginning use in mid-adolescence, were at increased risk for a range of negative outcomes including: poor respiratory, periodontal and mental health; decline in cognitive function; sub-par education and employment achievement; and difficulties in social and intimate relationships. With regard to the upcoming referendum it is particularly salient that all these harms occurred when cannabis use was illegal in Aotearoa-New Zealand.

It would appear that the level of harm-reduction achieved under a prohibition framework falls well short of what is desired or required. Further, due to the socially disfiguring and/or stigmatising nature of a criminal record, loss of multiple life opportunities can be expected for those with a conviction. If recreational cannabis use were legalised, the latter concern would be negated immediately. Legalisation would also help legitimise and facilitate strong educative and preventive efforts, particularly those aimed at young teenagers who carry especially high risk due to normative age-related changes in brain architecture. (For more detail see Patterns of recreational cannabis use in Aotearoa-New Zealand and their consequences: evidence to inform voters in the 2020 referendum or go to

However, this needs to be balanced against a theoretical risk of increased rates of use and abuse following legalisation. Early data from the U.S suggests this may be occurring. The drivers of this admittedly small effect (e.g. legalisation per se versus industrialisation and marketing) are unknown at this time. It is also too early to know anything about the stability or persistence of this trend.

But herein lies the rub. If harm minimisation were truly the goal, and this was best achieved via prohibition, then the two most commonly used legal substance in New Zealand – alcohol and tobacco – would probably be outlawed. Both have large scientific literatures attesting to the multiple harms associated with their use. Alongside this, many ‘natural experiments’ over the last century have shown that legal prohibition has failed when applied to alcohol, and many authorities now acknowledge that the ‘War on Drugs’ has been lost.

This then begs a bigger question. Where would the evidence lead if we adopted a first principles approach to harm minimisation for all substances (licit and illicit)? I would anticipate some very challenging questions – and uncomfortable answers – regarding the validity of our current approach. Four months ago I would have thought serious debate about this larger issue was unlikely any time soon. I am not sure this still needs to be the case in the new global reality. However, due to the many uncertainties that still lie ahead it is now more likely that the public’s appetite for such conversations will be reduced, albeit for perfectly understandable (instinctive) but nevertheless non-rational reasons (e.g., fear). This would be a shame.

COVID-19 has turned the world as we knew it upside down. At the same time it has revealed the critical importance of the scientific approach and robust evidence.  If we were consistent we would also rely heavily on science and evidence when dealing with other pressing (aka ‘wicked’) social issues, including substance (mis) use.

One final reflection. Maybe COVID-19 will help clarify just how pernicious the post-truth, post-fact zeitgeist has been for society.  If that came to pass, future trade-offs are likely to be more balanced and ultimately more effective in reducing harm – and in promoting societal wellbeing.