Risk of self-harm or suicide associated with specific drug use disorders, 2004-2016: a population-based cohort study

Background and Aims Drug use disorders are associated with increased risk of self-harm. Risk differences associated with specific types of drug use disorders are yet to be comprehensively reported. This study aimed to examine the risk of self-harm or suicide associated with different drug use disorders in Hong Kong. Design Population-based cohort study. Setting The Clinical Data Analysis and Reporting System (CDARS) managed by the Hong Kong Hospital Authority. Participants Cases were people ages 10 years or older who visited a hospital Accident and Emergency department between 1 January, 2004 and 31 December, 2016 with any of 10 specific drug use disorders (comprising opioid; ketamine; methamphetamine; sedative, hypnotic, or anxiolytic; amphetamine or related stimulant; cocaine; cannabis; hallucinogen; unspecified or other drug; and polydrug). Each case was matched with two controls, selected from a subset of people in CDARS sharing the same gender, age and psychiatric profile. A total of 8270 cases and 16 540 matched controls were included. Measurements Incidence and adjusted hazard ratio (aHR) of subsequent self-harm or suicide for each specific drug use disorder were estimated. Findings The most prevalent drug use disorder was opioid use disorder (2523; 30.51%) and the least prevalent was hallucinogen use disorder (77; 0.93%). The crude incidence of self-harm or suicide ranged from 26.57 (95% CI, 14.23-44.55) per 1000 person-years for cannabis use disorder to 91.97 (77.32-108.37) for polydrug use disorder. The highest risk of self-harm or suicide was observed in ketamine (aHR, 16.36; 95% CI, 11.03-24.29) and opioid (15.97; 10.73-23.23) use disorders. Conclusions In Hong Kong, all types of drug use disorders appear to be significantly associated with increased risk of self-harm or suicide, but risk levels vary by type of drug use disorder.