This study aimed to identify the patient characteristics, comorbidities, risk factors, and means of the self-harm of patients who attempt self-harm in and outside of a hospital, and to determine the characteristics of death by suicide among survival and death patient groups in South Korea. This study used data from the Korean National Hospital Discharge In-depth Injury Survey conducted from 2007 to 2019. In total, 7192 outpatient participants and 43 inpatient participants performed self-harm. Frequency analysis, chi-square tests, Fisher’s exact test, and logistic regression analysis were performed using STATA, version 15.0 (StataCorp), and statistical significance was set at 5%. Thirty-one inpatients who performed self-harm survived, and 12 died. Among male inpatients, the older they were, the higher the rates of self-harm and mortality rates due to falls and poisoning if they had comorbidities and financial problems. In addition, the rate of self-harm attempts within a short period after hospitalization was high. Our evidence of the characteristics of patients who performed self-harm in the hospital and the influencing factors of self-harm can be used as primary data for predicting patients at a high risk of self-harm and for creating preventative policies to reduce the risk of self-harm among inpatients in South Korea.

Self-harm is an action that intentionally injures oneself and is divided into self-injury with suicidal intention (suicide attempt) and non-suicidal self-injury, which does not involve suicidal intention [1]. Patients who self-harm are 56.8 times more likely to die by suicide than the general population [2], and patients with non-suicidal self-injury are three times more likely to attempt suicide in the future [3]. This suggests that all self-harm behaviors should be considered a risk factors for suicide, regardless of suicidal intention [2].According to the '2021 White Paper on Suicide Prevention,' suicide is the leading cause of death among teenagers and 20s in Korea, and in 2019, the suicide rate of 10-24-year-old in Korea was 1.8 times higher than the average of OECD member countries [4]. Male adolescents are more successful in suicide than female adolescents, whereas female adolescents are more likely to have suicidal ideation or plans [5]. However, the male-female ratio of youth suicide rates in Korea decreased from 1.2 times in 2018 to 1.0 times in 2019 [2,4]. Meanwhile, worldwide, the suicide rate among those aged 15-19 years is higher than that of those aged 10-14 years, and the suicide rate rapidly increases with age in the late teens [6]. Such suicide-related characteristics according to sex and age should be considered when planning suicide prevention strategies for adolescents.In 2019, of the suicidal methods taken among adolescents aged 10-25 years who died by suicide in Korea, jumping accounts for 38.5%, hanging for 37.4%, and gas poisoning for 14% [4]. It has been reported that the suicide rate among Korean adolescents increases as they use lethal methods of suicide [7],