Background Psychiatric disorders are established risk factors for self-harm. However, variation in risk of self-harm by specific psychiatric disorder, stratified by gender and age, is rarely examined using population representative samples. This study aims to investigate the risk of self-harm following the diagnosis of different psychiatric disorders based on inpatient records retrieved from the Hong Kong Clinical Data Analysis and Reporting System (CDARS). Method A cohort of 86,353 people with a first-recorded diagnosis of depression, alcohol abuse/dependence, personality disorders, bipolar disorders, anxiety disorders, schizophrenia, or substance abuse/dependence, along with 134,857 matched controls, were followed between 2000 and 2010. For each diagnostic category, a Cox proportional hazard regression model was fitted to estimate the adjusted hazard ratio (aHR) (95% confidence intervals) of associated self-harm, adjusting for gender, age, admission time, district of residence, and comorbidities. Outcomes The personality disorders and substance abuse/dependence groups had the highest self-harm incidences of 3,174 and 3,018 per 100,000 patient-years, respectively. The highest risk of self-harm was found in the substance abuse/dependence group (aHR, 9·6; 95% CI, 8·4-11·0), followed by the groups with personality disorders (3·7; 2·8-4·9) and alcohol abuse/dependence (3·2; 2·9-3·7). When stratified by gender and age, the highest risk was found in substance abuse/dependence group for both genders (female: aHR, 7·7; 95% CI, 6·0-9·8; male: 10·5; 95% CI, 8·9-12·4) and all age groups (adolescent: aHR, 9·6; 95% CI, 7·2-12·7; young: 10·2; 95% CI, 8·4-12·3; middle-aged: 11·2; 95% CI, 8·0-15·6; Elderly: 3·2; 95% CI, 1·7-6·1). Interpretation First-recorded diagnosis of psychiatric disorders were significantly associated with elevated risks of subsequent self-harm. The associations varied considerably by diagnostic categories across gender-age subgroups. This finding highlighted the needs to develop more efficient and targeted preventive measures in psychiatric care management. Specific attention should be paid to demographic characteristics linked to increased risk within the same diagnostic category
