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.