Risk of self-harm and suicide in people with mental disorders and the associations with psychiatric comorbidity burden in Hong Kong : a population-based study

Abstract

Introduction Mental disorders (MDs) are of substantial global prevalence and have significant implications for disability and pre-mature mortality, primarily attributed to suicide and self-harm. This study aimed to investigate the risks of self-harm and suicide among individuals with MDs compared to those without, while examining the impact of psychiatric comorbidities and evaluating how multiple comorbidities affect the likelihood of these outcomes and their combined effect.

Methods Data from public healthcare services in Hong Kong spanning from January 1, 2006 to December 31, 2021 were utilized to analyze the self-harm and suicide risks associated with 11 specific categories of MDs among individuals in psychiatric inpatient and outpatient settings. Patients with MD diagnoses were compared to those without, with the latter group randomly selected from 20% of data from general outpatient primary care clinics. Statistical analyses, including Cox proportional hazard models, were used to estimate hazard ratios by MD and by psychiatric comorbidity. Confounding factors were adjusted for the age, sex and Charlson Comorbidity Index score, and subgroup analyses stratified by sex and age group (12-24, 25-44, 45-64 and > 65) were conducted. A sensitivity analysis by using a narrow self-harm definition (International Classification of Diseases 10th revision codes X60-X69) was performed for robustness.

Results A total of 316,102 patients with MDs and 824,591 patients without MDs were included in this study. An elevated self-harm and suicide risk was identified across all MD categories. Individuals with MDs exhibited a 3.05-fold increased risk of self-harm (95% CI 2.97 – 3.14) and a 6.97-fold increased risk of suicide (95% CI 6.45–7.54). We found that substance use disorder (SUD) (adjusted hazard ratio (aHR) 7.60, 95% CI 7.16–8.07), alcohol use disorder (AUD) (aHR 5.63, 95% CI 5.17–6.13), and personality disorders (aHR 5.23, 95% CI 4.36–6.28) were the highest risk of self-harm behaviour. Schizophrenia-spectrum disorder (SSD) is the highest risk for suicide (aHR 12.39, 95% CI 11.17–13.74), followed by SUD (aHR 11.30, 95% CI 9.48–13.46) and bipolar disorder (aHR 11.09, 95% CI 8.78–14.00). Males and females with MDs had a similar overall risk for both self-harm and suicide. The age group of 45-64-year-old exhibited the highest risk for both outcomes (self-harm aHR 3.77; suicide aHR 7.61). SUD comorbid with SSD has the highest risk of self-harm and suicide risk among different psychiatric comorbidity combinations with an aHR of 5.39 (95% CI 3.67 - 7.91) and 14.54 (95% CI 1.35–156.42) respectively.

Conclusion We identified that patients with various MDs exhibited elevated risks of self-harm and suicide, with SUD, AUD, and personality disorders showing the highest self-harm risks, while SSD, SUD, and bipolar disorder presented the greatest suicide risks. individuals aged 45-64 were at the highest risk for both outcomes. These findings highlight the need for further research on this age group, including the development of prediction models and randomized controlled trials to address these risks.