Risk Factors for Suicidal Ideation of the General Population

Recently, suicide is a major mental health issue in Korea (1). Suicide is the fourth highest cause of death in Korea with an average of 42 incidents a day (2). The identification of the risk factors of suicide has therefore become a crucial target in health policy.

A number of studies have examined suicide risk factors, prevention and the ways of reducing suicide-related behaviors. Previous studies have shown that suicide is the result of a multifaceted range of social, psychiatric and biological factors, and one or more of these variables may affect suicidal behaviors by complex mechanisms (3-5). Although there are many studies of suicidality and suicide risk factors in people with various mental disorders (6, 7), the findings of these researches may not necessarily generalize to the general population.

The problem of suicide is no longer limited to some psychiatric patients, and consequently the assessment of suicidality and preparing for its appropriate management in the community has important clinical implications (8). For the sake of the mental health of the community, it is therefore necessary to conduct a study of risk factors for suicide idea in the general population sample at large rather than just on those psychiatric patients receiving hospital inpatient or outpatient services. This will enable us to plan suicide prevention strategies not only for psychiatric patients, but also for people in the general community, who do not visit mental health services.

Thus, the main purpose of the present study was to assess suicidal ideation and related factors in a community sample, which was representative of the general population in an urban area of Korea.

Table 1 summarizes the sociodemographic, psychological characteristics, and sleep durations of total participants. Two hundred ninety four participants (29.4%) showed significant depressive symptom, defined as high CES-D group (≥ 16) as the previous study (9). Participants with the CES-D score less than 16 were classified as low CES-D group (Table 1). Comparisons between the high and low CES-D groups are summarized in Table 1. Compared with the low CES-D group, the high CES-D group was significantly older (mean ages: 41.8 ± 12.0 vs 38.7 ± 11.39, t = -3.814, P < 0.001), had a higher ratio of females (55.4% vs 47.7%, χ² = 4.933, P = 0.026), were more likely to have a family history of psychiatric disorder (9.9% vs 2.7%, χ² = 23.369, P < 0.001), were more likely to be married (77.7% vs 71.2%, χ² = 4.196, P = 0.041), and were more religious (64.6% vs 52.3%, χ² = 12.862, P < 0.001). The high CES-D group also scored higher on the BSI (6.3 ± 6.5 vs 3.4 ± 3.8, t = -7.148, P < 0.001), the STAXI (38.1 ± 9.0 vs 33.0 ± 7.1, t = -8.648, P < 0.001) and the BIS (64.4 ± 8.7 vs 59.7 ± 9.2, t = -7.634, P < 0.001).

The results of the partial correlation analysis are shown in Table 2. After adjusting for age and gender, the scores on the BSI were found to be positively correlated with the CES-D, STAXI and BIS scores (r = 0.245; P < 0.001, r = 0.344; P < 0.001, and r = 0.152; P < 0.001, respectively). The BSI scores showed no significant correlation with sleep duration on weekday (r = -0.044, P = 0.167).

Table 2
Partial correlations controlling for age and gender between suicidal ideation and other variables (n = 1,000)

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The International Classification of Sleep Disorders (21) defines a 'short sleeper' as someone who sleeps five hours or less a day and a 'long sleeper' as someone sleeping 10 hours or more a day. In the present study, we classified short and long sleepers into an abnormal sleep duration group. The regression analysis revealed that higher scores on the BSI were related with higher scores on the STAXI and on the CES-D, the presence of a family history of psychiatric illness and abnormal sleep duration (Table 3; F = 45.449, adjusted R² = 0.151, P < 0.001, P < 0.001, P = 0.001, and P = 0.008, respectively). The regression model with high CES-D group showed stronger predictive power, in which higher scores on the BSI were associated with higher scores on the STAXI, an abnormal sleep duration and the presence of a family history of psychiatric illness (Table 4; F = 38.092, adjusted R² = 0.275, P < 0.001, P < 0.001, and P < 0.001, respectively).

Table 3
Stepwise linear regression model predicting suicidal ideation in total sample (n = 1,000)

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Table 4
Stepwise linear regression model predicting higher suicidal ideation in high CES-D group (n = 294)

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This study investigated the relationships between suicide ideation and associated factors in a community population in an urban area of Korea. The results showed that subjective depressive mood, high anger, abnormal sleep duration and a family history of psychiatric illness were related to suicide idea in general population. These relationships were more prominent in the high CES-D group.

The mean CES-D score for the total participants was 11.6 ± 7.3, and 29.4% showed clinically significant levels of depressive symptoms (scores of 16 or higher in CES-D), and this finding is consistent with those reported in previous studies (22). Just as others have done, we proposed the relationship between depression and suicide ideation. From the study done in the past (20), 95% of people who commit suicide have a diagnosis of mental disorder, and 80% of those with a mental disorder are diagnosed as suffering from depression.

In current study, a positive correlation of anger with suicide idea was also found. Previous studies have demonstrated possible relationships between higher anger and suicidality (23, 24). The present study increases our knowledge about the relationship between anger and suicide idea. In Asian culture, the expression of anger tends to be usually discouraged. This represents a major challenge to Koreans who experience anger, but feel pressure to express and manage the emotion in culturally acceptable ways. Lee et al. (23) showed that anger is an important marker for people, who may be at risk of engaging in suicidal behavior. A similar finding was also reported in a Turkish study (24), in which suppressed anger was shown to increase suicidal thoughts. In the present study, intense feelings and tendency to suppress anger might increase suicidal thought.

Previous studies have shown that individuals who suffer from insomnia or sleep disturbance could be at greater risk of depression and committing suicide (25-27). In the current study, we conducted the question on sleep duration which is a feasible additional risk factor for suicide. While many studies have shown that sleep disorders are highly associated with suicide (28-31), no study has been conducted on the association between suicide idea and sleep duration. Looking at the studies of relativity of sleep only commented relation of insomnia or subjective sleep problem and suicide idea done in the past (30-33), it has never used parametric measure of suicidal ideation with scales. In this study, abnormal sleep duration (five hours or less or 10 hr or more) was related with higher suicidal ideation.

There was a study on the association of hypersomnia with suicidality the past (27), but the previous study only focused on the increasing rate of suicides in depressed patients with hypersomnia. To the best of knowledge, this is the first study which showed the relationship between long sleep duration and suicide idea. One possible explanation of this association between long sleep duration and suicide idea is that hypersomnia may be mainly related to depression with atypical features (20). Another possible reason is that hypersomnia or long sleep can be associated with sleep disorders, such as sleep apnea and narcolepsy, which are known to be related to depression (30, 31). Moreover, the finding that sleep disorders such as nightmare's can be related to increased suicidality after controlling for depression (28) suggests that suicide may be directly related to sleep disturbances and not always mediated by depression.

In current study, the presence of a family history of psychiatric illness (within their second-degree relatives) was related to higher suicide idea. Psychiatric patients with history of psychiatric illness in their biological family are known to respond less well to treatment, leading to an unfavorable prognosis (34). A feasible explanation is that this unfavorable treatment response can be related to higher suicidality, and the other interpretation imply that suicide can be significantly controlled by biological and genetic factors. This common notion is supported by a number of research findings suggesting biological mechanisms of suicide such as genetic factors (35, 36). In addition, Roy and Segal (37) found higher rates of concordance for suicidality in monozygotic than in dizygotic twins.

Impulsiveness measured by BIS scores used in the present study, did not predict high suicide ideation. In a past research, impulsiveness has been considered to be one of the important factors associated with suicide (38). One possible explanation for this inconsistency is that we related impulsiveness to suicidal ideation rather than actual attempted suicide. This finding suggests that impulsiveness may be strongly related to suicidal behaviors rather than suicide thoughts. More research is needed before any firm conclusions can be drawn about the relationships between impulsiveness and suicidality.

The present study has several limitations. Firstly, the methodology involved subjects completing self-report questionnaires without structured or semi-structured interviews. This precluded an objective assessment of subject's psychiatric status. Secondly, we relied entirely on measure of sleep duration, which was also self-reported. This made it impossible to identify secondary symptoms of sleep disorders may have been related to suicidal ideation. Thirdly, the present study design was cross-sectional, and hence limits our ability to assess causal associations between suicidal ideation and associated risk factors. Thus longitudinal studies are needed to clarify causality.

In spite of several limitations, the current study is meaningful, because it assessed risk factors for high suicide idea in a general urban population using representative samples randomly recruited from city districts and matched equally in terms of gender and age group.

In conclusion, our results suggest that depressive mood, high anger, short or long sleep duration and a family history of psychiatric illness might be risk factors for suicide idea in the general population. Therefore, mental health professionals might pay special attention not only to one's subjective mood state (including depressiveness and anger), also sleep duration and family history of psychiatric illness to evaluate suicide risk factors in a community.