Risk of Self-Harm in Patients with Trichotillomania: A Population-Based Cohort Study

Background: This study aimed to investigate whether individuals with trichotillomania (TTM) are at a higher risk of engaging in self-harm behaviors compared to those without TTM. Methods: In this matched cohort study, we analyzed electronic health records of all patients admitted to public hospitals in Hong Kong from 1 January 1993 to 31 December 2022. We identified a TTM cohort of 285 patients and a comparison cohort of 285 individuals. All participants were followed up until they received a diagnosis of self-harm, died from other causes, or until the end of 2023, whichever came first. To assess the risk of self-harm following TTM onset, Cox proportional hazards regression models were applied. Results: Throughout the 30-year study period, the number of individuals who exhibited self-harm behavior in the TTM and comparison groups was 8 (2.8%) and 8 (2.8%), respectively. The TTM and comparison groups had similar proportions of subjects who inflicted self-harm (χ2 = 0.00, p = 0.977). The incidence of self-harm was 26.00 and 26.92 per 10,000 person-years in the TTM and comparison groups, respectively. Compared with the comparison group, the adjusted hazard ratio for self-harm in the TTM group was 1.44 (95% confidence interval, 0.45–4.61). Conclusions: TTM is not associated with an increased risk of self-harm. Future research is necessary to replicate our findings and more fully elucidate the potential unique risk factors for self-harm in these patients.