The World Health Organization has reported that over 800,000 people commit suicide each year (1). According to the Organisation for Economic Co-operation and Development (OECD), the Republic of Korea (hereafter, Korea) has shown the highest suicide rate among its member countries since 2003. In 2015, 13,513 people died from suicide in Korea (2). The fact that the suicide rate in Korea, which was 26.5 per 100,000 inhabitants in 2015 (2), is twice as high as the average suicide rate of all OECD nations, which was 13.1 per 100,000 inhabitants in 2013 (3), has drawn research interest (4). In Europe, a systemic review showed that the estimated cost per depression case was €3,826, and the cost of affective disorders amounted to €106 billion in 2004 (5); mortality ascribed to suicide accounted for about 4% of the costs of depression (6). In addition to the well-known long-lasting effects on the bereaved, suicide is a social problem in the economic perspective, as it is the second leading cause of death in people aged 15–29 years, the age group that is entering or preparing to enter a community main workforce (1). Therefore, developing prevention and treatment strategies has become urgent, pressing research focus worldwide.

Not only developing an effective intervention for suicidal patients under hospital-level care but also reforming higher-level social systems is essential; intensive monitoring for patients under treatment of depression during high-risk periods of suicide would necessitate service reorganization and incremental expenditures (7). Ultimately, this approach shall involve a system-wise initiative with the engagement of policymakers and appropriate allocation of currently available economic and human resources. A study showed that a positive impact on suicide reduction, a 33% decrease in relative risk in the U.S. Air Force personnel was accomplished by policy changes in a military system (8). Moreover, current interventional programs and policies on suicide are often multifaceted and rarely evaluated (9); some of the treatments or prevention strategies are either not cost-effective or surely not perfect to prevent suicide (5). Therefore, taking substantial social expenditure into consideration, it is necessary to review the economic feasibility of present strategies as well. For adequate assignment of resources to the right places, efficacy evaluation, and eventually new policy making and strategy development, it is important to understand characteristics of the populations that we are fighting for. In the economic aspect, several studies have addressed the necessity of “tailored” intervention to meet particular needs according to different populations. These interventions would potentially be more effective if applied to specific groups, for example, with depression (10), with a lack of social support and low socioeconomic status (11), or in poverty (12).

To achieve this goal, it is critical to specify the characteristics of the target population on which suicide prevention is to be applied. Since suicidality usually accompanies psychiatric disorders, for establishing anti-suicidal strategies, people with suicidal behavior can be approached in a dichotomized way—a group in a hospital setting and another in a community—although a clear-cut division is not possible. However, to the best of our knowledge, most studies about suicidal behavior have evaluated patients visiting hospitals or using their medical or insurance records. Even articles dealing with community-dwelling populations are mostly restricted to the elderly suicidal population, probably owing to increasing research interest due to a higher suicide rate among them (13). Few studies have examined characteristics of a general community-dwelling population with suicidality, irrespective of age, gender, medical or psychiatric conditions, or scrutinized their differences from a hospital-based study population. Science has developed by questioning conventional ideas taken for granted, and, in such a context, we raised a doubt on a view that hospital visitors and community dwellers might simply reflect a difference in severity of psychopathology. First, some of community-dwelling suicidal ideators with high clinical severity may prefer not to receive hospital care because of stigma surrounding psychiatric treatment; by contrast, hypochondriacal patients or personality disorder patients showing excessive attention-getting behavior may be found more among hospital visitors to a degree disproportionate to their clinical severity. Second, as suicidal ideation is included only in the diagnostic criteria of major depressive episode among entire psychiatric disorders, it cannot be presumed that suicidal ideators in the community are also clinically less severe in psychopathology other than depression such as anxiety, substance use, or impulsivity. Therefore, it is justifiable to perform a comparison study of these 2 groups but also necessary to verify what has been accepted without proof with scientific methods.

The present study used a dataset from the Korean Cohort for the Model Predicting a Suicide and Suicide-related Behavior (K-COMPASS) study to report baseline characteristics of hospital-based and community-based populations with suicidality and differences between the 2 groups. Further, we aimed to propose tailored strategies for suicide prevention depending on the elucidated features in each group.

To our knowledge, this is the first cross-sectional study performing a direct comparison of characteristics of 2 suicidal populations, a CC and a HC, which aims to eventually and practically serve as a guide for efficient allocation of limited anti-suicidal resources according to the group differences. In comparison analyses using descriptive statistics, elderly people, single households, and those with low socioeconomic status comprised a larger percentage of the CC group than the HC group. The HC group presented clinically more severe features: on histories, more suicidal behaviors and psychiatric diagnosis confirmed by K-MINI and, on rating scales, higher scores of PHQ-9, BAI, AUDIT-K, and BIS-11. When stress related to social relationships using SRS was addressed, the HC group was under more stress from close family and workplace. By comparison, considering various stress sources in Stress Questionnaire for KNHANES-SF, the main causes of stress were illness or injury of oneself or others or financial difficulty for the CC group and interpersonal relationships for the HC group.

In the present study, the results fell into 2 categories: clinical and social aspects. First, the finding that the clinical condition of subjects in the HC group was more serious than that of subjects in the CC group was partly expected because patients with more severe depression, anxiety, alcoholism, and impulsivity were more likely to be noticed and brought to hospitals by people around them instead of being referred to community mental health centers or visit psychiatric clinics by themselves to seek help for relieving their distress rapidly, usually for pharmacotherapy. However, it should be noted that all the levels of measured psychopathology other than depression in the HC group were also higher even though suicidal ideation was not a symptom required for diagnosis of psychiatric disorders related to anxiety, alcohol use, and impulse control problems; hospital visitors with suicidal ideation tended to have more severe, comorbid psychiatric conditions, which justifies screening for other mental disorders for them. It is noteworthy that the HC group had a relatively larger proportion of patients with a history of early trauma, too. Evidence continues to accumulate indicating that childhood trauma leaves a profound impact on brain development, which would result in the increased likelihood of psychopathology in adults through biological processes such as alterations in Hypothalamic-Pituitary-Adrenal (HPA) axis or reductions in platelet brain-derived neurotrophic factor (BDNF) (24). In addition, victims of childhood trauma have been reported to be vulnerable to psychiatric illnesses associated with impulsivity such as substance dependence and suicidal behavior (25), which is thought to be mediated by malfunction of brain inhibitory processes such as serotonergic hypofunction and HPA axis dysfunction, consequences of prolonged exposure to trauma (26). Our results appear to support this hypothesis that history of early trauma may contribute to development of suicidal ideation via psychopathology such as depression, alcoholism, and impulsivity.

In the social aspect, the second part of the results, we showed novel findings. In comparison with the HC group, senior citizens living alone with lower socioeconomic status comprised a larger percentage of the CC group. First, a recent study from Korea showed that people in late adulthood are more likely to perceive a psychiatric disorder as a stigma. Thus, their infrequent utilization of psychiatric resources is more strongly influenced by this perceived stigma than young or middle-aged groups (27). A prejudice against psychiatry may have been a treatment barrier for mental illness. Partly, the outcome about age distribution depended on the way the subjects were recruited. Some of the subjects in the CC group were already members of community mental health centers at the time of enrollment. Adolescents or young adults might face difficulty going to the centers because of their schools or jobs, and thus they were less likely to be screened there. Instead, relatively old people without regular daytime occupations probably had more chances to participate in activities in the center, which could increase their possibility to be included in the CC group. Also, the recruiters visited flophouses where usually only one person resides; compared to adults, adolescents were highly unlikely to live alone. Second, people with low socioeconomic status who lack ability to pay the NHI are covered with the Medical Aid Program (MAP), which subsidize medical fees for those under financial difficulty. However, compared with the NHI, the MAP applies low permissible limit in medical expenses and, as a result, does not often provide a high quality of medical care. It is possible that the poor subjects in the CC group were unable to receive sufficient psychiatric care, which resulted in a greater proportion of uninsured individuals in this group. Alternatively, people with low income may have opted not to spend their money on psychiatric care; they may have preferred to expend on non-psychiatric medical illnesses causing tangible, physical distress. Third, compared with the CC, the HC group had a lower proportion of single households, which implies that family members' involvement and encouragement make at-risk people enter and stay for psychiatric care in hospitals. This inference is in line with the literature reporting limited family support as a risk factor for nonadherence to psychotropic medications (28). In addition, a higher percentage of single households in the CC group (51.7%) than in the Korean general population (27.2%) (29) may reflect high rates of divorce in patients with depressive disorders (30) and their increased suicide rates due to social isolation (31). In addition, community social capital, which includes a concept of standards of reciprocity and mutual aid in a community among its various attributes, plays an important, positive role in mental health (3233). Regarding suicidality, regions with a high degree of community social capital were reported to have lower suicide rates (33). As community social capital stands for the importance of social relationship, living alone or absence of marital relationship is presumably associated with insufficient community social capital and consequently increased suicidality. The findings of the present study that the CC group had less stress from social relationships may ironically reflect their solitude as well.

All these suicidal people do need care of any kind, and the undertones of our findings in potential intervention are the possibility and importance of tailored approaches to managements of suicidal risk addressing the characteristics of a population. From the results in the HC group, for the suicidal population visiting hospitals, more clinically focused intervention would be essential to reduce suicidal risk considering their higher severity based on suicidal-related histories, psychiatric diagnosis, and clinical ratings. This inference is in line with a recent systemic review reporting that clozapine and lithium have substantial evidences of anti-suicidal effects, and pharmacotherapy and psychotherapy of depression, a major risk factor for suicide, plays an important role in suicide prevention (34). One of the important issues in Korean psychiatric service is neglect in psychotherapy. Because of low medical fees for psychotherapy, clinical scale-oriented hospital evaluation entailing cost, and excessive patient workload resulting from low medical insurance fee, pharmacotherapy is a general trend with the role of psychotherapy being ignored (35) especially in tertiary hospitals. Actualization of psychotherapeutic fees in the NHI for suicidal patients will boost use of psychotherapy contributing to reduction of suicide rates.

On the other hand, the outcomes from the CC group indicate that efficient investment of anti-suicidal resources targeting people that are older, maintain socially less connection, or have lower income would be profitable. First, because the CC group has an older population, proactive community outreach programs such as screening visits to senior citizens' community centers or senior care centers will be effective in early identifying community-dwelling suicidal people and hopefully in involving them in hospital care. A suicide prevention campaign for elderly individuals especially deserves urgent attention because owing to the physical weakness associated with old age (reflected in the higher frequency of medical illnesses in the CC group in our study), even a suicidal attempt of low lethality such as drug/chemical overdose or use of a sharp object (36) may prove lethal for them. Second, the CC group has a higher proportion of people living alone, which implies their limited social interaction. To offer opportunities to develop social relationship such as participation in a community mental health center may be helpful for reducing suicidal risk; this will be achieved by investing financial resources to improve current facilities or build new ones and increase human resources to expand present programs or develop new activities. According to a recent systemic review, community-based interventions had the ability to reduce suicide, except for severely ill psychiatric patients, and, for the elderly, there was evidence that screening for depression along with follow-up at the community had an effect on reducing suicide risk (34). In addition, a study showed that culturally informed intervention on an underserved minority women with suicide risk had resulted in reducing suicidal ideation and depressive symptoms (37); therefore, it is inferred that social support projects, in particular, at a culturally similar community level will be potentially beneficial for suicide prevention. The third feature of the CC group is a larger proportion of unemployment, and thus improving their economic conditions has to be considered. Numerous studies have reported that suicide mortality was increased by unemployment in many developed countries (3839), which implies that local community job fairs or governmental investment on employment promotion projects might be a good start point to reduce a suicide rate of the jobless people with suicidal ideation in the community. Our suggestion is in line with a proposal from a previous research endorsing financial support for the elderly to reduce their suicide rate since the economic standard resulted in a significant influence on the suicide rate in those aged 65 years or older (34). Furthermore, rationalization of the MAP for psychiatric treatment, a more direct way of providing economic support, will be necessary to deliver a quality of care as high as that of the NHI. However, despite the necessity of socioeconomic support, it has to be emphasized that those that are not receiving psychiatric treatment may need to be referred from community mental health centers to psychiatrists for evaluation or management, considering our finding that 40.0% suffered from current major depressive episode and 72.5% are currently at suicide risk.

The present study has several limitations. First, the cross-sectional nature of the study design does not allow any causal inference because the possibility of reverse causality. Second, the cohorts were heterogeneous themselves; the composition of the 2 cohorts was likely to be affected by the proportions of recruitment channels, but the exact proportion of each channel was unavailable. In case of the HC group, the subjects recruited at emergency departments or psychiatric wards were more likely to have imminent suicidal risk, and yet those enrolled at outpatient clinics may have had less severe suicidality. Therefore, the clinical severity of the results might have depended, partly, on the recruiting way. For the CC group, the participants under case management may have had more psychiatric treatment history, those included through screening visits to underdeveloped areas may have belonged to a lower socioeconomic status, and those referred from other public agencies may have exhibited more acute symptoms. It is possible that the enrollment routes affected characteristics of the cohorts, and thus they did not reflect actual characteristics of the target populations. Third, we divided suicidal population as either hospital-based or community-based population; however, these 2 groups are not mutually exclusive. Some of the subjects in the HC could have been recruited to the CC group if they had been noticed in the community. On the contrary, subjects in the CC group, especially those under case management, have possibly ever received psychiatric treatment in a hospital; therefore, although they were included in the CC group, they may share similar characteristics with those in the HC group. Fourth, we suggested socioeconomic interventions on suicidality in a community population about which there is a paucity of studies, let alone randomized controlled trials, for example, whether employment promotion decreases suicidality. Fifth, all the medical centers in the study are tertiary hospitals, which usually have a more severe, refractory patient pool. The relatively high scores in the scales in the HC group may be due to a bias in our study samples. Sixth, although we selected the participating hospitals spread all over the country to not be regionally biased, they were not a statistically representative sample of the target population.

Despite these limitations, the present study presents meaningful findings that warrant more detailed comments. First, this is the first study to perform a direct comparison between hospital visitors and community-dwellers with suicidality on a nationwide scale. Second, this study included cities of various sizes throughout Korea to represent the target population for the CC group. The cities ranged from Iksan, Jeollabuk-do, a small city with a population of 301,337 to Seoul, a metropolis with a population of 9,931,412 as of February 2017, minimizing a bias in urbanization (40).

In conclusion, this cross-sectional, epidemiologic study identified the distinguishing characteristics of study samples: the HC group with clinically greater severity and the CC group with a larger percentage of old people living alone with low income. The finding indicates the necessity of more clinical support for hospital visitors and more socioeconomic aid for community-dwellers showing suicidality. Further studies using a large sample size are greatly required, and intervention emphasizing psychiatric treatment for the HC group and socioeconomic support for the CC group are warranted to confirm efficacy of tailored interventions on each group. Lastly, because studies on suicide prevention lack randomized-controlled trials (34), these gold-standard approaches are not only necessary but also urgent.