What Have Been the Public Health Impacts of Cannabis Legalisation in the USA? A Review of Evidence on Adverse and Beneficial Effects

Abstract

To summarise empirical research on the adverse and beneficial public health impacts of cannabis legalisation in states in the USA. The most consistent finding from surveys of drug use is that the legalisation of medical cannabis has so far not had an effect on rates of use or cannabis use disorders among youth, but it has increased the frequency of use among adult cannabis users. There are conflicting findings on the impact of legalisation of medical and recreational cannabis use on the following: cannabis use disorders in adults, rates of motor vehicle accidents in which the driver was impaired by cannabis, rates of suicide, and opioid-related harms. The legalisation of recreational cannabis use has increased emergency room attendances for cannabis-related medical conditions (acute adverse psychological effects, hyperemesis, and accidental poisoning of children). There is no evidence to date on the impact of medical or recreational legalisation on the prevalence of mental disorders such as psychoses, depression, and anxiety. There is suggestive evidence that cannabis legalisation is associated with a range of public health consequences. However, current evidence is limited in the capacity to confidently conclude that these changes are the result of cannabis legalisation. The impacts on public health may take some years to become apparent.