Analysis of all non-fatal self-harm cases in an urban area of Japan during pre- and peri-pandemic periods of COVID-19: a population-based study.

Background: This study aimed to examine population-based characteristics of non-fatal self-harm in an urban area during pre- and peri-pandemic periods of COVID-19 by sex, age, and severity of self-harm, using pre-hospital medical emergency records.

Methods: We used a registry of all pre-hospital medical records of self-harm cases that occurred in Kawasaki City, Japan, between January 2018 and December 2021. Adjusted incidence rate ratios (IRRs) with 95% confidence intervals (CIs) were calculated using Poisson regression models with the log-transformed population by year, sex, age group, and ward as an offset term.

Results: During the 4-year study period, 1,534 patients were transported by ambulance due to non-fatal self-harm and were alive on arrival at the hospital. Among women, the number of non-fatal self-harm cases increased by 1.2-fold in 2021 compared with that in 2018. The incidence rate of "severe" non-fatal self-harm among men aged 19 years or younger in 2021 (IRR 4.82, 95% CI 1.25-18.65) and that among women aged 50-59 years in 2020 (IRR 2.51, 95% CI 1.06-5.95) significantly increased compared with that 2018 and 2019. The incidence rate of "mild" self-harm among women aged 20-29 years tended to be higher in 2021 than in 2018 and 2019 (IRR 1.42, 95% CI 0.95-2.12, P = 0.085).

Conclusions: During the peri-pandemic period of COVID-19, the incidence rate of "severe" non-fatal self-harm among men aged 19 years or younger and women aged 50-59 years, as well as that of "mild" self-harm among women aged 20-29 years, sharply increased compared with that during the pre-pandemic period. Our findings suggest that in urban areas during public health crises such as a pandemic, it is important to take measures to reduce the risk of non-fatal self-harm in young women, in addition to strengthening counseling and support for young women at risk for completed suicide.