Can cannabis kill? Characteristics of deaths following cannabis use in England (1998-2020)

Abstract

Background: Cannabis is the most widely used illegal drug but is rarely considered a causal factor in death.

Aims: This study aimed to understand trends in deaths in England where cannabinoids were detected at post-mortem, and to evaluate the clinical utility of post-mortem cannabinoid concentrations in coronial investigations.

Methods: Deaths with cannabinoid detections reported to the National Programme on Substance Abuse Deaths (NPSAD) were extracted and analysed.

Results: From 1998 to 2011, on average 7% of all cases reported to NPSAD had a cannabinoid detected (n = 110 deaths per year), rising to 18% in 2020 (n = 350). Death following cannabis use alone was rare (4% of cases, n = 136/3455). Traumatic injury was the prevalent underlying cause in these cases (62%, n = 84/136), with cannabis toxicity cited in a single case. Polydrug use was evident in most cases (96%, n = 3319/3455), with acute drug toxicity the prevalent underlying cause (74%, n = 2458/3319). Cardiac complications were the most cited physiological underlying cause of death (4%, n = 144/3455). The median average Δ9-tetrahydrocannabinol post-mortem blood concentrations were several magnitudes lower than previously reported median blood concentrations in living users (cannabis alone: 4.3 µg/L; cannabis in combination with other drugs: 3.5 µg/L).

Conclusions: Risk of death due to cannabis toxicity is negligible. However, cannabis can prove fatal in circumstances with risk of traumatic physical injury, or in individuals with cardiac pathophysiologies. These indirect harms need careful consideration and further study to better elucidate the role cannabis plays in drug-related mortality. Furthermore, the relevance of cannabinoid quantifications in determining cause of death in coronial investigations is limited.

Keywords: Cannabis; THC; cannabinoids; drug-related death; toxicity; Δ9-tetrahydrocannabinol.

Figure 1.

(a) Number of deaths reported to NPSAD from England (1998–2020) with cannabis detections at post-mortem. As the average period between death and conclusion of coronial inquests for drug-related deaths is 7–10 months, further deaths from 2020 are anticipated to be reported. The number of deaths projected to still be received (dashed bar area) has been calculated based upon these previous jurisdiction reporting trends. (b) Proportion of deaths with cannabis detections at post-mortem reported to NPSAD from England (1998–2020). When normalised against total NPSAD reporting in England over the same time period, the increase in deaths with cannabis detections remains, demonstrating that there has been a proportional rise in their occurrence.

Figure 2.

Implication rate of cannabis in deaths reported to NPSAD from England (1998–2020). Note that whilst the 2020 implication rate has been calculated, this is subject to change pending receiving additional reports.

Figure 3.

Number of drugs co-detected in cannabis cases by year. Note that whilst the 2020 data has been included, this is subject to change pending receiving additional reports.

Figure 4.

Median detected post-mortem levels of THC in cases where quantifications were performed; 2020 data has been excluded due to the low number of cases with THC quantifications provided at the time of writing.

Figure 5.

Proportion of cannabis cases with co-detected substances over time. Note that whilst the 2020 data has been included, this is subject to change pending receiving additional reports.

Figure 6.

(a) Age at death and (b) decile of deprivation of decedents with cannabinoids detected at post-mortem. Note that whilst the 2020 data has been included, this is subject to change pending receiving additional reports.