Prevalence and risk factors for repetition of non-fatal self-harm in Hong Kong, 2002–2016: A population-based cohort study

Background: A history of self-harm is strongly associated with future self-harm attempts. Large-scale Asian cohort studies examining risk factors for repeated self-harm are lacking. This paper reports on annual prevalence, cumulative risk, annual risk of non-fatal self-harm repetition, and risk factors among Hong Kong patients with a history of self-harm. Methods: The Hong Kong Clinical Data Analysis and Reporting System (CDARS) provided all accident & emergency department and inpatient self-harm records between Jan 1, 2002 and Dec 31, 2016. Demographic and clinical characteristics were extracted. Annual prevalence, over-time cumulative and annual risks of non-fatal self-harm repetition were estimated, and the adjusted hazard ratios (HR; plus 95% CIs) of putative risk factors associated with repetition were estimated using Wei-Lin-Weissfeld (WLW) generalization of the Cox model for recurrent event analysis. Findings: There were 127,801 self-harm episodes by 99,116 individuals. Annual prevalence of repeated self-harm, of all self-harms, ranged from 7•36% to 28•71% during the study period. Risk of self-harm repetition within one year of the index event was 14•25% (95% CI, 14•04%-14•46%). People with four or more previous self-harm episodes carried the highest risk of self-harm repetition (adjusted HR 4•81 [95% CI 4•46–5•18]). Significant risk factors for non-fatal self-harm repetition included male gender (1•08 [1•05–1•11]), older age (65+ years) (1•07 [1•01–1•13]), social welfare for payment (1•30 [1•27–1•34]), psychiatric admission (1•60 [1•50–1•72]), self-injury only (1•19 [1•15–1•23]), self-injury combined with self-poisoning (1•38 [1•24–1•53]), depression and bipolar disorders (1•09 [1•04–1•14]), personality disorders (1•18 [1•06–1•32]), substance misuse (1•31 [1•27–1•36]), and asthma (1•18 [1•02–1•36]). Interpretation: Hong Kong self-harm patients with non-fatal self-harm events should be supported by effective, timely and ongoing aftercare plans based on their risk profiles, to reduce risk of self-harm reoccurrence. Funding: Research Grants Council, General Research Funding: 17611619.