Potential benefits

Irrespective of the regulatory controls or retail strategies enacted by each jurisdiction, every global example of legalisation has made cannabis products more available, more affordable and more easily advertised to potential consumers.^{Reference Smart and Pacula1,Reference Hall, Stjepanović, Dawson and Leung2} Potential benefits include generation of substantial taxable revenue and specific reductions in cannabis-related crimes that have historically been used to overpolice minorities and communities of colour.^{Reference Hall, Stjepanović, Dawson and Leung2} Arguments have also been made regarding the potential for legalisation to reduce stigma directed against people who use cannabis products and to address any current barriers people may encounter when seeking appropriate treatment or harm reduction measures for problematic cannabis use. These benefits, however, must be balanced against any potential adverse public health considerations mediated via post-legalisation changes in individual and population-level consumption patterns.

Potential risks

Notwithstanding the benefits of product quality assurance that occur when moving to an unadulterated and regulated market, almost all jurisdictions report a post-legalisation increase in cannabis consumption at the population level and, by extension, increased rates of cannabis addiction.^{Reference Zellers, Ross, Saunders, Ellingson, Anderson and Corley3} Many areas have also observed significantly increased cannabis product potency, the persistence of unregulated or ‘black’ markets despite legalisation and substantial diversification in the types of cannabis products available for different routes of administration.^{Reference Hall, Stjepanović, Dawson and Leung2} Demand on the UK National Health Service (NHS) is currently at an all-time high and there is mounting evidence of post-legalisation increases in cannabis-related emergency department visits in peer countries.^{Reference Smart and Pacula1,Reference Hall, Stjepanović, Dawson and Leung2,Reference Myran, Pugliese, Tanuseputro, Cantor, Rhodes and Taljaard4} Global reports also suggest that several cannabis-related mental and physical health harms may increase after legalisation, with these likely to be concentrated among teenagers, young adults, pregnant women and those with existing mental disorders.^{Reference Solmi, De Toffol, Kim, Choi, Stubbs and Thompson5} Increased availability following legalisation has been linked to increased rates of psychosis and cannabis-involved pregnancies,^{Reference Myran, Pugliese, Tanuseputro, Cantor, Rhodes and Taljaard4,Reference Manthey, Jacobsen, Hayer, Kalke, López-Pelayo and Pons-Cabrera6} with this association more pronounced among people who have been less exposed to cannabis products prior to legalisation. Given that cannabis use is a significant risk factor for people, with and without underlying psychosis, to transition to schizophrenia spectrum disorders, any significant post-legalisation increase in availability, potency or consumption may have a substantial impact on population-level mental health.^{Reference Myran, Harrison, Pugliese, Solmi, Anderson and Fiedorowicz7} Depending on the legalisation model adopted there are also reports of significant increases in cannabis-related road traffic accidents and spikes in accidental child poisonings.^{Reference Hall, Stjepanović, Dawson and Leung2,Reference Myran, Tanuseputro, Auger, Konikoff, Talarico and Finkelstein8,Reference Kilmer, Rivera-Aguirre, Queirolo, Ramirez and Cerdá9}

If the UK policy or ‘Overton window’ opens wide enough for legalisation of cannabis products to become a viable policy option, the additional pressures likely placed on the UK health and social care system, and in particular the mental health and addiction treatment systems, may further stretch the currently limited resources in these settings and exacerbate identified underlying issues, including chronic underfunding and lack of an adequately trained workforce.

‘Legalisation’

The term ‘legalisation’ is neither binary nor refers to a singular policy decision. Different models of legalisation, with different decisions relating to factors such as commercialisation and risk mitigation, are thus likely to result in very different scenarios with respect to health outcomes.^{Reference Hall, Stjepanović, Dawson and Leung2} Consequently, there is likely to be a theoretical statute by which recreational cannabis legalisation in the UK, on aggregate, reduces the overall level of societal harm it inflicts compared with the current legal framework. However, this hypothetical legislation would almost certainly require extremely strict regulatory sales practices and hypothecated funding from generated revenue to combat any increase in cannabis-related harms.^{Reference Smart and Pacula1,Reference Hall, Stjepanović, Dawson and Leung2} Future shifts in political power, alongside innovative practices of industries that legally produce and market addictive products, mean any new legislation is susceptible to commercial or governmental attempts at deregulation and market expansion. The requirement of a guarantee that these laws and any public health protections would not be ‘watered down’ would appear to be in tension with the concept of UK parliamentary sovereignty. Given the extreme unlikelihood of wholesale repeal of a legalisation statute – there are currently no international examples of ‘re-banning’ similar products or indeed of significantly tightening regulatory controls once the decision has been made to legalise – this factor should be included in considerations of potential longer-term harm to the nation's health. As both benefits and harms disproportionately affect people in society who typically experience minoritisation, equitable consideration needs to be given to these groups, particularly as the political landscape, corporate influence, product innovation and advocate priorities change over time.

Stating a blanket position as a ‘yes or no’ to cannabis product ‘legalisation’ fails to consider the nuance of a multitude of policy decisions that would have an impact on the consequences of any proposed legislation. Consequently, balancing the risks and benefits is necessarily a complex process. Further, decisions relating to commercialisation, proposed mitigations against potential harms and the ability to amend any provisions after statute passage all alter the risk–benefit equation of such a decision. As further international evidence emerges relating to the short-, medium- and longer-term consequences of legalisation across other jurisdictions some of these issues may become clearer. At the current moment in time, a substantial number of policy questions remain unanswered and pressure on the UK mental health and addiction treatment systems is at an all-time high. This limits the current UK government's ability to draft a piece of future-proofed legislation that would definitively result in the sustained protection of the nation's health in an era of legally sanctioned supply and consumption.