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A drug harms ranking study for Aotearoa New Zealand

drugs on table

Dr Rose Crossin Department of Population Health – University of Otago, Christchurch

Drug harm is a significant public health burden in Aotearoa New Zealand (1,2,3); though harms are not evenly distributed across the population. Māori are the indigenous population of Aotearoa New Zealand, making up approximately 17% of the total population, and have a notably younger age demographic. Māori are overrepresented in drug harm, including adverse events associated with synthetic cannabinoids (4), an elevated likelihood of arrest and conviction for cannabis-related offences (5,6), and disproportionate alcohol-related harm (7). These outcomes reflect cumulative disadvantage for Māori, arising as a result of colonisation, and relating to inequities within the health and mental health systems, discrimination, and poorer socioeconomic outcomes. The profile of drug harm is also likely to differ for adolescents due to factors such as potential interference with education and employment, social norms relating to drug use, and traits such as curiosity and sensation seeking (8,9). In Aotearoa New Zealand, adolescent use of alcohol, tobacco and cannabis appears to have stabilised following a long period of decline; however, binge drinking in adolescents remains high by international standards and this is associated with increased self-reported harm (8). For these reasons, we decided that there was value in undertaking a drug harms ranking study for Aotearoa New Zealand, based on the study led by David Nutt, which was applied in the UK, and then subsequently in the EU and Australia (10,11,12).

There were some key differences in the way we designed our study. Firstly, we decided to use the MCDA approach to assess harms across the total population, and then separately for youth and for Māori. The paper recently published contains the total population and youth findings, with the Māori-specific study likely to be published in 2024. A panel of 23 experts was convened, with diverse expertise including justice, police, medicine, policy and community services. Of this, a sub-set of the panel (8 people) formed a youth-specific panel; this group considered drug harm specifically to youth aged 12-17. The panel agreed on 17 harm criteria; some key differences were that we merged two of the original criteria (drug-specific and drug-related impairment of mental functioning), and we created two new criteria to better reflect a Māori worldview. These new criteria were “spiritual harm” (a harm to self) and “intergenerational harm” (a harm to others). Originally, we intended to use these solely for the Māori specific part of the study, however, the expert panel saw value in applying them to the total population and to youth, and in the workshops these criteria generated robust and useful conversation. The criteria were systematically applied to 23 drug types, including alcohol, using a ranking, scoring and weighting process. The drug list had been amended for our local context e.g. we included kava but did not include crack cocaine. Harms were considered in the context of local policy settings.

Our results indicated that alcohol was the most harmful drug in Aotearoa New Zealand. This was for both the total population and for youth. Alcohol scored proportionally higher in ‘harm to others’ than in ‘harms to person using the drug’. The two highest contributing criteria to alcohol’s harm scores were ‘drug related mortality’ and ‘community damage’. It is important to note that alcohol scored highly across many of the 17 criteria, hence resulting in the cumulatively high overall harm score; this is reflective of the breadth of harm associated with alcohol. The results were not due to alcohol being the most prevalent drug used in Aotearoa New Zealand, and assumptions were based on harm accruing to an individual using that drug in Aotearoa New Zealand, with ‘typical’ use patterns.

When considering the contribution of individual harm criteria to overall harm scores, differences were observed between the total population and youth. For instance, family adversities had a higher contribution to harm for the total population, and drug-related damage tended to account for more harm in youth (e.g., unwanted sexual activity, accidents to the person using the drug). Cannabis was evaluated as more harmful to youth, ranking sixth for youth, compared with ninth for the overall population. Youth ratings were higher in the broader harms to self category, with larger contributions from criteria such as impairment in function and drug-related mortality. This study is, to the best of our knowledge, the first drug harms ranking study specific to youth. The different results from the total population suggest that this was valuable to undertake.

Some of our results have surprised people, particularly those for cocaine and illegal fentanyls. Our study did not adjust for prevalence, we assessed as per harm to a ‘typical’ person who uses the drug in Aotearoa New Zealand. The score for cocaine reflects the market in Aotearoa New Zealand (i.e. relatively low supply with high prices), which influences the ‘typical’ user and use patterns. It’s worthwhile noting though this caused quite a bit of debate in the workshops and so we undertook sensitivity testing, though it did not materially change the findings. Fentanyl rated highly in harm to the person using the drug, particularly driven by the high mortality score. But it ranked lower than some drugs on harm to others. This is acknowledged as a limitation in the study, because while the mortality risks of fentanyl were widely understood by the panel members, very limited local data may have meant that some local fentanyl-related harms, such as community damage, were less salient for our expert panel. It is essential to be prepared for these high-potency opioids increasing in the local drug market, and therefore, investment in harm reduction needs to be proactive. This should include overdose prevention measures such as supervised injecting facilities and take-home naloxone programmes, both of which have extensive evidence of efficacy in reducing harm (13,14,15). Given that Aotearoa New Zealand’s drug market may change, integrated and responsive systems for rapid surveillance, and engagement with affected communities is vital. Our study findings reflect Aotearoa New Zealand and our understanding of harm at a point in time, but we know fentanyl could significantly increase community harm if it was more present in our drug market and therefore we need to be prepared.

Aotearoa’s two most widely used legal drugs, alcohol and tobacco, were found to cause the first and fourth-largest amount of harm overall. The results also identified a mismatch between harmfulness and legal status. We found a spread of harmfulness amongst a number of illegal Class A drugs, with some causing a lot of harm, and others very little. In some cases, the criminal penalties for using these drugs don’t match the level of societal harm they actually cause. We highlight the harm being created by Aotearoa New Zealand’s drug policies. Our study identified that a significant proportion of drug harm arises from the legal status of the drug, rather from the drug itself. This includes harms to the individual such as loss of employment and relationships, along with harms to others relating to crime and family adversities. This suggests we need to reconsider our policy settings to reduce overall drug harm, and also target our interventions to better consider how best to support family, friends and communities.

For many drugs, current policy responses contributed to higher ratings on specific criteria, with one example being criminalisation due to drug possession and use. Therefore, for drugs such as cannabis, the higher harm scores are largely a function of current drug policy settings. For those affected by drug misuse, prosecution for possession acts as an additional stressor while reducing future opportunities. Māori are disproportionally affected by criminalisation of people who use drugs; although Māori make up 17% of the population of Aotearoa New Zealand, 48% of those convicted of drug possession are Māori, demonstrating clearly that drug laws are being enforced in a racially biased manner (6). Our recommendation is that a review of Aotearoa New Zealand’s drug policy is needed, which considers a health-based approach to managing drug use and structural determinants of drug harm, including any negative effects of the current prohibition-based drug policy. Drug related harms and existing strategies to prevent drug availability and use also tend to impact the most vulnerable populations. Therefore, implementing evidence-based harm reduction measures, in addition to focusing on population level risk factors, such as socioeconomic deprivation, may be a more effective way of reducing drug-related harm (16). While we acknowledge the limitations of the MCDA method, these local results can be used to inform drug policy, funding decisions, treatment, and education, and, ultimately, to reduce harm and associated inequities.

Full citation: Crossin, R., Cleland, L., Wilkins, C., Rychert, M., Adamson, S., Potiki, T., … & Boden, J. (2023). The New Zealand drug harms ranking study: A multi-criteria decision analysis. Journal of Psychopharmacology, 02698811231182012.

Funding disclosure: This study was funded by a Health Research Council grant, awarded to Dr. Rose Crossin (University of Otago), and a University of Otago Research Grant, awarded to Dr. Rose Crossin and Prof. Joe Boden.


1. McFadden M, Bellamore L and MacDonald B (2022) The New Zealand Illicit Drug Harm Index 2020. Wellington: Ministry of Health.

2. New Zealand Law Commission (2010) Alcohol in our lives: curbing the harm. Available at:

3. Ministry of Health, Health and Independence Report 2017. The Director-General of Health’s Annual Report on the State of Public Health. 2018, Ministry of Health: Wellington.

4. Robson H, Braund R, Glass M, et al. (2021) Synthetic cannabis: adverse events reported to the New Zealand Pharmacovigilance Centre. Clinical toxicology (Philadelphia, Pa.) 59(6): 472-479.

5. Fergusson DM, Swain-Campbell NR and Horwood LJ (2003) Arrests and convictions for cannabis related offences in a New Zealand birth cohort. Drug and Alcohol Dependence 70(1): 53-63.

6. New Zealand Drug Foundation (2022) Drugs snapshot shows system grossly failing Māori across the board. Available at: (accessed 1 May 2023).

7. Alcohol Healthwatch (2023) Harm to Māori. Available at:āori (accessed February 21 2023).

8. Ball J, Crossin R, Boden J, et al. (2022a) Long-term trends in adolescent alcohol, tobacco and cannabis use and emerging substance use issues in Aotearoa New Zealand. Journal of the Royal Society of New Zealand. DOI: 10.1080/03036758.2022.2060266. 1-22.

9. Brumback T, Thompson W, Cummins K, et al. (2021) Psychosocial predictors of substance use in adolescents and young adults: Longitudinal risk and protective factors. Addictive Behaviors 121: 106985.

10. Nutt D, King LA and Phillips L (2010) Drug harms in the UK: a multicriteria decision analysis. The Lancet (British edition) 376(9752): 1558-1565.

11. van Amsterdam J, Nutt D, Phillips L, et al. (2015b) European rating of drug harms. Journal of psychopharmacology (Oxford) 29(6): 655-660.

12. Bonomo Y, Norman A, Biondo S, et al. (2019) The Australian drug harms ranking study. Journal of psychopharmacology (Oxford) 33(7): 759-768.

13. Levengood TW, Yoon GH, Davoust MJ, et al. (2021) Supervised injection facilities as harm reduction: a systematic review. American Journal of Preventive Medicine 61(5): 738-749.

14. Monds LA, Bravo M, Mills L, et al. (2022) The Overdose Response with Take Home Naloxone (ORTHN) project: Evaluation of health worker training, attitudes and perceptions. Drug and alcohol review. DOI: 10.1111/dar.13474.

15. Tse WC, Djordjevic F, Borja V, et al. (2022) Does naloxone provision lead to increased substance use? A systematic review to assess if there is evidence of a ‘moral hazard’ associated with naloxone supply. International Journal of Drug Policy 100: 103513.

16. Holland A, Stevens A, Harris M, et al. (2022) Analysis of the UK Government’s 10-Year Drugs Strategy—a resource for practitioners and policymakers. Journal of Public Health.

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