Risk of self-harm after the diagnosis of psychiatric disorders in Hong Kong, 2000-10: a nested case-control study.

BACKGROUND: Psychiatric disorders are established risk factors for self-harm. However, variation in the risk of self-harm by specific psychiatric disorder and stratified by gender and age is rarely examined in population-representative samples. This study aimed to investigate the risk of self-harm following diagnosis of different psychiatric disorders in an Asian population, through a review of inpatient records retrieved from the Hong Kong Clinical Data Analysis and Reporting System (CDARS).
METHODS: For this nested case-control study, the inpatient data of people admitted for any reason to Hong Kong public hospitals, between Jan 1, 2000, and Dec 31, 2010, were extracted from CDARS. Cases were people aged 10 years or older who had been admitted to inpatient care with a first-listed record of psychiatric disorder during the study period. The seven psychiatric disorders of interest were: depression, alcohol misuse or dependence, personality disorders, bipolar disorders, anxiety disorders, schizophrenia, and substance misuse or dependence. Two control patients were matched per case from a subsample of all individuals with the same gender, age, and admission time (ie, same calendar year and month), who did not have any record of the psychiatric disorders of interest. Any patients with a history of self-harm diagnosis before, or at the same time as, the first diagnosis of psychiatric disorder (cases) or admission (controls), were excluded. For each diagnostic category, a Cox proportional hazard regression model was fitted to estimate the adjusted hazard ratio (HR; plus 95% CIs) of associated self-harm, adjusting for gender, age, control-matched admission time, 20 districts of residence, physical comorbidities established as risk factors for self-harm (diabetes, asthma, migraine, epilepsy, HIV, and cancer), and presence of the six other psychiatric disorders. We repeated this analysis in subgroups stratified by gender (male and female) and by age (adolescent, 10-24 years; young adult, 25-44 years; middle-aged, 45-64 years; and older people, ≥65 years).
FINDINGS: Between 2000 and 2010, we followed up a cohort of 86 353 people with a first-recorded diagnosis of a psychiatric disorder of interest, and 134 857 matched controls. The highest risk of self-harm was observed in patients with substance misuse or dependence (adjusted HR vs matched controls, 9·6 [95% CI 8·4-11·0]), followed by those with personality disorders (3·7 [2·8-4·9]) and alcohol misuse or dependence (3·2 [2·9-3·7]). When stratified by gender and age, the highest risk of self-harm behaviour was found in the substance misuse or dependence group for both genders (for female patients: adjusted HR vs matched controls, 7·7 [6·0-9·8]; and for male patients, 10·5 [8·9-12·4]), and for all age groups (adolescent: 9·6 [7·2-12·7]; young adults: 10·2 [8·4-12·3]; middle-aged: 11·2 [8·0-15·6], and older people: 3·2 [1·7-6·1]).
INTERPRETATION: First-recorded diagnoses of psychiatric disorders were significantly associated with an elevated risk of subsequent self-harm. The associations varied considerably by diagnostic categories across gender and age subgroups. Our findings highlight the need to develop more efficient and targeted preventive measures in psychiatric care management, with specific attention to demographic characteristics linked to increased risk within the same diagnostic category. FUNDING: None.