Suicide accounts for the largest proportion of socioeconomic disease burden caused by diseases and accidents [1]. Suicide among highly productive people in their 20s to 40s was found to be the largest socioeconomic burden [2,3]. In particular, depression is a mental disorder closely related to suicide, and it also affects the suicide rate, which has been steadily increasing since 2000 [4]. The number of suicides in Korea in 2022 was 12,906, recording a suicide rate of 25.1 per 100,000 people [5]. In addition, the suicide rate, which is one of the standards showing the quality of life of Koreans, has ranked first among OECD countries since 2003. When comparing the age-standardized suicide rates (per 100,000 OECD standard population) of OECD member countries in 2020, Korea’s suicide rate was 24.1, the highest among OECD member countries [6], which is more than twice as high as the OECD average mortality rate of 11.0, highlighting the importance and effectiveness of policies to prevent suicide, an avoidable cause of death.

In Korea, the government has been actively pursuing policies to reduce the suicide rate [7]. Various national policies have been pursued, including the enactment of the Suicide Prevention Act in 2011, the cancellation of the re-registration of paraquat, a highly toxic pesticide, the ban on the sale of highly toxic pesticides and the opening of the Central Suicide Prevention Center in 2012, the implementation of a post-suicide management program based on emergency rooms in 2013, and the announcement of suicide reporting guidelines. In addition, efforts have been made to lower the suicide rate through active private suicide prevention projects [5]. The suicide rate in 2023 is expected to be 27.3 per 100,000 people, the highest since 2018 [8].

Suicide is the result of a complex interaction between various systems surrounding an individual, as well as the biological, cognitive, and psycho-emotional characteristics of the individual [9]. In addition, suicide is very complex and heterogeneous, including mental illness, economic, and cultural factors [10]. In general, suicidal ideas lead to suicide plans and suicide attempts, and suicide attempts lead to suicide [11]. Understanding the dynamics of suicide attempts and identifying factors that influence them is an essential component in developing effective prevention strategies [12]. Therefore, research addressing the multifaceted nature of suicide attempts, including mental health, economic, and cultural factors, is absolutely necessary.

Mental and behavioral disorders are widely recognized as major risk factors for suicide [11,13-16]. People with serious mental disorders are at significantly higher risk for suicidal behavior [17]. Among those who self-harm, those diagnosed with mental and behavioral disorders represent a particularly vulnerable group who require intensive intervention and support [18,19]. Persistent attempts at self-harm, coupled with complex mental health problems, complicate the treatment and recovery pathways [20].

The presence of comorbid diseases such as diabetes and cardiovascular disease in mental and behavioral disorders can lead to problems such as complicated diagnosis and treatment, longer hospital stay, and greater consumption of medical resources [21]. However, it also has a positive effect in accelerating patient access to medical institutions such as hospitalization or meeting medical professionals for treatment of comorbid diseases [22]. This can increase the effectiveness of managing mental and behavioral disorders and reduce the risk of suicide. However, although there are many previous studies that have investigated the relationship between suicide attempts and mental behavioral disorders [23-26], there are not many studies that have analyzed the differences according to comorbidities accompanying mental behavioral disorders.

Because of the high prevalence of comorbidities among patients who attempt self-harm, it is essential to thoroughly investigate comorbidities. The interaction between mental and behavioral disorders and various comorbidities may provide important insights into risk and protective factors that influence self-harm behavior. Therefore, this study aims to investigate the characteristics of hospitalized patients diagnosed with mental and behavioral disorders that cause self-harm and understand the characteristics of suicide attempts and suicides in these patients. In addition, we aim to derive implications for clinical perspectives and non-clinical management methods to reduce suicide among suicide attempters by identifying the characteristics of comorbidities.

We attempted to identify the characteristics of patients diagnosed with mental and behavioral disorders and the importance of comorbidities. We obtained interesting results in patients hospitalized after attempted self-harm.

The main age group of self-harming patients diagnosed with mental and behavioral disorders was found to be in their 20s and 30s. In fact, the main age group of self-harming patients diagnosed with mental disorders is usually reported to be in their 20s and early 30s [28-30]. In this study, the proportion of female self-harming patients diagnosed with mental disorders was high, so it is necessary to classify young people and women with mental disorders as a major risk group for attempted selfharm and pay attention to them. In addition, depression stands out as a representative mental disorder in self-harming patients, and the main onset of depression is concentrated in young women in their 20s, so it is necessary to establish policies that take this into account when managing cases of mental and behavioral disorders.

Previous studies have shown that the high suicide rate among Korean women in their 20s and 30s is mainly due to mental health issues such as depression and anxiety disorders. In particular, the social stigma surrounding mental health and the difficulty in accessing treatment can be obstacles for young women to deal with their emotions or seek help. Korean society has traditionally placed high expectations on women. In addition to the burden of marriage and childbirth, the job market is very competitive, and expectations of social success can cause great stress, which can lead to suicide attempts. Due to this tendency, women have been shown to have interpersonal conflicts and stress related to suicidal thoughts. In addition, studies in Japan and Australia, as well as Korea, have shown that temporary/unstable employment is a factor that is significantly related to suicide among female workers. However, according to previous studies, the overall risk of repeated self-harm attempts is similar for men and women, and it is also reported that men are at a higher risk than women in the 20-24 age group [31]. In addition, women have been reported to have a higher risk of relapse than drug overdose [31]. Since there are various factors related to suicide, such as demographic and lifestyle factors, future research on suicide needs to be subdivided by gender, age, and socioeconomic level, along with the presence of comorbidities.

Seasonal variation in suicide rates is a well-documented phenomenon. Most studies worldwide explain that suicides peak in spring, reach a second peak in fall, and decline in winter, mainly in men and the elderly [32]. In this study, seasonal differences were clearly observed in patients who attempted suicide due to mental illness, but there were differences from previous studies. The number of suicide attempts increased from winter to spring, but unlike previous studies, there was a relative decrease in fall. Seasonal affective disorder is a seasonal pattern of recurrent major depressive episodes that occur most frequently in fall or winter and are alleviated in spring [33]. Unlike seasonal affective disorders, other forms of recurrent depression, such as bipolar or unipolar depression, occur regardless of the time of year [34]. Therefore, it may be difficult to explain the seasonal variation in the results of this study as being because many of the subjects have affective disorders. In the future, in-depth analysis of factors that show seasonal variation by limiting cases of suicide attempters to mental disorders will be necessary.

In addition, most patients with mental illness who attempted suicide harm themselves at home (66.74%), and considering that the number of patients who harm themselves increases from winter to spring, it is judged that they are more likely to harm themselves at home during a period when their activity level is relatively low. In addition, many self-harm attempts occur in daily life (while walking, sitting, or standing, etc.) (66.57%). Therefore, it is necessary to introduce a life intervention program so that these patients can sufficiently engage in outdoor activities and receive sufficient sunlight after discharge from the hospital. In addition to in-hospital treatment, it is thought that receiving psychological treatment outside the hospital [35] and lifestyle interventions such as increasing exercise or outdoor activities will also have an effect on improving the patient’s condition [36]. Therefore, continuous attention from people around the patient in their daily lives after discharge and continuous monitoring using ICT technologies such as lifestyle monitoring apps are necessary. In particular, it has been difficult to meet the increased demand with existing mental health-related services during the COVID-19 pandemic [37-39]. This has led to the search for alternative solutions such as digital mental health services. That is, it includes a wide range of mental health services, including suicide prevention, mental health promotion, and drug and alcohol addiction treatment, and since services are provided through digital platforms such as websites and mobile applications, it provides both convenience and accessibility in monitoring [40-42]. In other word, from a medical policy perspective, IoT technology and other non-clinical management methods can be used to enable continuous, non-contact management. In addition, only 49% of self-harming patients with mental illness responded that the reason for their self-harm was mental problems, even though they were diagnosed with mental and behavioral disorders as their primary diagnosis. In other words, there are cases where they are not aware of their mental problems. In addition, about 23% of cases judged conflict with friends or family as the reason for their self-harm. The reason for attempted self-harm may arise from issues other than mental problems, but clinical judgment and treatment through differentiation of the exact reason are necessary.

The majority (88%) of patients with mental illness who commit suicide are discharged after their condition improves, and the mortality rate is analyzed to be low. As in previous studies, damage due to poisoning (61.34%) was analyzed as the most common method of self-harm in this study [31]. The results are the same as previous studies [17], which found that the most common method of suicide was poisoning. Other mechanisms included stab wounds, laceration, and amputation (22.33%). The reason for the relatively low mortality rate of patients diagnosed with mental and behavioral disorders seems to be that most of the substances used in self-harm attempts are antiepileptic drugs, sedatives, sleeping pills, anti-Parkinson drugs, and psychoactive drugs that are considered to be commonly taken. Repeated suicide attempts due to easily accessible drugs such as the patient’s usual medications or sleeping pills can eventually lead to death. In addition, there are cases where mentally ill self-harming patients do not come to the emergency room immediately after self-harming, but visit the hospital as an outpatient (7.9%). Such factors can lead to repeated self-harming attempts and chronic suicide attempts, so immediate hospital visits after self-harming, along with medication management and monitoring of the patient’s condition, require attention and education from those around them.

The most common disease code for the primary diagnosis of patients with a psychiatric diagnosis was F322 (severe depressive episode without psychotic symptoms), and many cases had depression-related codes. 46.78% of self-harming patients with a psychiatric disorder had one or more comorbidities. The most common codes for comorbidities excluding the principal diagnosis code after hospitalization were T424 (benzodiazepine), T426 (other antiepileptic and sedative-hypnotic drugs), T432 (other and unspecified antidepressants), and S619 (open wound of wrist and hand, part unspecified). Chronic diseases such as hypertension and diabetes mellitus also exist, but they do not account for a large proportion. It was analyzed that comorbidities are a factor affecting the length of hospital stay, and when the number of comorbidities increases by one, the length of hospital stay increases by 1.889 days. Other studies have shown similar results, with hospitalization lengths longer in patients with comorbid mental disorders than in patients without comorbid mental disorders [43,44].

It was confirmed that the length of hospital stay significantly increases when surgery is performed or co-morbidities are present. The age group 50s had the longest average length of stay, but the average length of stay was 20.52 days, which was higher than the average length of stay for all age groups. When the addictive substance was alcohol, the average length of stay was 71.57 days. It is reported that the majority of self-harm patients often arrive at the hospital in an alcoholic state. Alcohol management is a very important point in patients who attempt self-harm or have mental illness. In addition, although the length of stay varied depending on the addictive substance, the length of stay for other and unspecified chemicals and toxic substances was 41.06 days, indicating that management of suicide attempts due to addiction is very necessary. From a clinical perspective, it will be necessary to treat mental illness, behavioral disorders, and complications in a multidisciplinary manner simultaneously to increase treatment effectiveness and reduce suicidal thoughts or attempts.

Among factors related to suicide, those with physical illness are more likely to attempt suicide, and the mortality rate is high due to not only suicide attempts but also drug abuse, smoking, alcohol abuse, and poor self-care [45,46]. Chronic diseases that limit physical function or movement, such as stroke, Parkinson’s disorder, and oral cancer, and mental disorders such as depression, bipolar disorder, and schizophrenia show consistent associations with suicide [47]. The comorbidities with the highest suicide risk were mental and behavioral disorders, and cardiovascular disease was also high [48]. This result was confirmed in the results of this study. It is also reported that the risk of suicide increases as the number of physical illnesses increases [49]. From a clinical perspective, comorbidity factors interact with social and economic factors to make clinical management more difficult, time-consuming, and resource intensive [50]. Therefore, it is necessary to identify comorbidities at the early stage of patient contact and establish a clinical treatment direction.

Despite producing these important results, this study has some limitations. First, we used the 2022 KNHDIS form Korea Disease Control and Prevention Agency. The data is about patients discharged from hospital. The population of data is patients discharged after hospitalization in a general hospital with more than 100 beds. Therefore, the characteristics of hospitals with less than 100 beds were not reflected. Therefore, it may be limited in explaining the characteristics of all self-harm that occurs in Korea. Second, sociological variables for patients are limited in this data, so there are limitations in utilizing various variables. Third, in this study, cases of self-harm in the hospital after hospitalization were excluded. This is a case that can occur in reality. Future research will also need to study these cases. Fourth, we excluded two cases with a length of stay of more than 31 days: 156 days and 366 days. If there are enough long-term patient cases exceeding 31 days, future studies including long-term hospitalized patients are also needed. Fifth, this study focused on patients diagnosed with a mental or behavioral disorder as their principal diagnosis after hospitalization. In the 2022 KNHDIS data, there are also other self-harm patients. Future research is also needed on other patient groups who do not have mental or behavioral disorders as their principal diagnosis. Sixth, the sampling design of KNHDIS is a complex sample survey, and it is recommended to do weighting for analysis. However, we analyzed the network analysis data using unweighted samples. We could not find an R package that could perform network analysis with complex sample survey data. Future research needs to conduct network analysis using weighted data. Finally, this study targeted patients who were hospitalized after attempted self-harm and diagnosed with mental and behavioral disorders (F00- F99) as the principal diagnosis code. Therefore, the disease code corresponding to mental and behavioral disorders) and poisoning and certain other consequences of externality may have emerged as major comorbidities. Therefore, it would be desirable to define S00-T98 and F00-F99 codes as one patient and conduct further research on related complications.

Despite these limitations, this study is very meaningful. In Korea, approximately 25% of adults are diagnosed with mental illness during their lifetime, and the rate of suicide attempts with mental illness is also very high. Therefore, in order to prevent suicide in people with mental and behavioral disorders, it is necessary to identify important characteristics related to suicide attempts and implement prevention and management methods, and continuous monitoring and psychological evaluation are necessary in their lives. In addition, it was confirmed how important it is to manage comorbidities in patients with mental illness who attempt self-harm. Ultimately, accurate treatment of patients with mental illness and reduction of comorbidities is a way to lower the social and clinical costs from self-harm.