Alcohol is one of the leading causes of the global burden of disease, and alcohol use disorders (AUDs) are known to be a major risk factor for suicide [1]. AUDs are the second most common psychiatric disorder among those exhibiting suicidal behaviors worldwide, following major depression [2]. Further, about 40% of patients with AUD have had at least one suicide attempt at some point [3]. A large cohort study conducted in Denmark indicated that suicide mortality was higher in patients with AUD than it was in any other psychiatric illness (unadjusted hazard ratio: 7.98) [4]. On the other hand, acute alcohol use(AAU) increases the risk of suicidal behavior, which indicates that alcohol consumption at the time of suicide is not merely a reflection of ongoing drinking problems [5]. Further, about 37% (10-69%) of suicide decedents and 40% (10-73%) of suicide attempters were found to have used alcohol at the time of the suicide attempt [2]. Several studies have examined the overlapping effect of AUD and AAU on suicide attempts [6]. One previous study suggested that individuals attempting suicide under the influence of alcohol were more likely to have AUD (30-49%) [7] and other studies found that the rate of AAU was higher in individuals with AUD in completed suicides (69% vs. 23%) [8] and in suicide attempts (83% vs. 31%) [9]. However, since the alcohol use patterns are often duplicated and it is difficult to distinguish clearly, there are few studies that separately examine the effects of the AUD and AAU on suicidal behavior.

The suicide rate in Korea is the second highest among the Organization for Economic Co-Operation and Development (OECD) member countries, with 25.8 deaths per 100,000 people, which is approximately 2.2 times higher than the OECD average of 11.6 deaths per 100,000 people [10]. Further, compared to western countries and other Asian countries, the suicide rates in Korea presented a sharper increase and stronger persistence. In Korea, which has such a high suicide rate, the per capita consumption of alcohol is 7.95 L, and the annual drinking rate of adults is close to 77%, which is far above the world average according to the WHO statistics published in 2014. This unusual alcohol use rate might allow to suggest the presence of a strong association with the high suicide rates in Korea. Although controversy still exists with the alcohol use pattern in relation to the risk factors for suicide reattempts, alcohol use has been known to be associated with repeated suicide attempts [11]. However, studies on the association between alcohol use pattern and suicide reattempts are lacking in Korea, and very little is known about the effect of alcohol use in prolonged risk of suicide reattempt.

In these context, we aimed to outline the transient and prolonged effects of alcohol use patterns on suicide attempters. The main objectives of the present study were: 1) to assess the characteristics of suicidal behaviors according to alcohol use patterns; 2) to compare the lethality and intent of suicide attempters by alcohol use patterns; 3) to investigate the prolonged risks of repeated suicide attempts by alcohol use patterns. To our knowledge, this is the first study to compare the characteristics of suicidal behaviors within groups according to non-overlapping patterns of alcohol use, using a Korean sample who have both high rates of suicide and alcohol consumption at the same time.

In the present study, we highlighted several important associations among characteristics of suicidal behaviors, risk of suicide reattempt, and alcohol use patterns among suicide attempters who visited emergency room. The present analysis revealed a high rate of incidence of AUD (n=355, 51.4%) in suicide attempters who visited the emergency room. This prominent association of alcohol with suicide behavior may be due to the cultural differences in alcohol drinking observed in Korea. The main findings of this study are as follows. First, we found that patients with AUD attempted suicide with more help seeking behaviors and had higher proportion of low medical lethality compared to not only NAU but also AAU group. Second, suicide attempters with AUD showed lower risk-rescue rating scores with a high rescue opportunity but suicide attempters with only AAU did not. Third, while AAU was not associated with the risk of future suicide reattempt before and after adjusting for other risk factors, AUD was related to higher risk of suicide reattempt compare to NAU and the increased risk was prolonged longer period.

This finding is consistent with those of previous studies that revealed that impulsive suicide attempts are more strongly associated with AUD than with AAU [18]. The present study also replicated previous studies that AUD was found to increase the risk of repeated suicide attempts [19], and previous suicide attempts in alcohol dependent patients increased the risk of subsequent suicide attempts [20]. While in line with prior work, the unique findings of this study are that the risk of suicide reattempts in patients with AUD was consistently high regardless of AAU, both before and after adjusting for other risk factors for repeated suicide attempt such as lethality and suicidal intent of the previous suicide attempt.

The results of this study reflect the fact that, among those with AUD, suicidal behavior is more related to the psychopathology of alcohol dependence, such as difficulty in impulse control. In the study, suicide attempts in patients with AUD tended to have low lethality and risk-rescue rating scores at baseline. Several previous studies have focused on this issue, and have reported that alcohol-related suicide attempts have low mortality and high risk of repeated suicide attempts. This tendency is called as “deliberate self-harm syndrome” [21]. Therefore, suicide attempts in those with AUD may be overlooked due to their low lethality, as revealed in the present study (e.g., there is a lower risk of complete suicide in patients with AUD). However, based on the present findings, it is suggested that suicide attempts in patients with AUD require more careful evaluation and intervention owing to the high risks of repetition.

Furthermore, we also found that the high risk of suicide reattempt for patients with AUD lasted for more than 60 months after the previous suicide attempt, while the same persisted for up to 36 months in patients with AAU. This suggests that AUD may have more extensive and long-lasting impacts on subsequent suicidal behavior. It is important to note that some mood disorders, one of the important risk factor of suicide attempts, may be caused by alcohol consumption and alcohol withdrawal, and it is often associated with chronic affective dysregulation [22]. Both aggression and depression are well-known risk factors for subsequent suicidal behavior in alcohol dependent individuals [23]. As has been noted by numerous studies, AUD may play a key role in recurrent suicidal behavior, through a number of mechanisms that exacerbate negative mood states and risky behaviors that promote suicidal behaviors [24]. On the other hand, some previous studies have explained the adverse consequences on brain development and executive function in patients with AUD due to a number of neurotransmitter hypofunctions [25]. Thus, neurobiological factors, including serotonergic mechanisms, may play a role in repeated suicide attempts in patients with AUD. The serotonin neurotransmission deficiency may be associated with impulsiveness and suicide attempts that accompany alcohol dependence [26]. It is well known that behaviors associated with prefrontal brain dysfunction in patients with AUD significantly predict not only the executive function system but also affective abnormalities [27]. These permanent and complex effects of AUD in suicide attempters may increase and sustain the risk of repeated suicide attempts.

The strengths of this register-based study include the large numbers of cases of suicide attempters included in the analysis and the use of a detailed questionnaire to collect information on alcohol use pattern and characteristics of suicidal behaviors. Additionally, we performed follow-up and analysis of suicide reattempts after adjusting the detailed variables over a sufficient periods of time, which has never been done before in Korea. The present study has a number of limitations that should be considered when interpreting the findings. First, the sample of the present study was limited to one university hospital in a specific area in Korea, which may limit the generalizability of the current findings. Second, there was a selection bias because we excluded several patients who refused to consent to psychiatric evaluation or were missing drinking information. Third, there is insufficient information on comorbid diseases (e.g., mood disorder, personality disorder) that may affect the progress of suicide attempters. Despite these limitations, this study made it possible to understand the relationships among the factors related to alcohol use patterns that affect suicidal behavior over time.

In conclusion, suicide attempters with AUD have been shown to have lower lethality of suicide attempt but higher risk of suicide reattempts in the future, regardless of alcohol use at the time of suicide attempt. The results of present study suggest that suicide attempters with AUD should be considered a high-risk group for future suicide reattempts, and careful attention should be paid to the development of a longerterm intervention program. Additionally, each suicide attempter needs to be evaluated carefully for AUD, regardless of whether they had consumed alcohol at the time of the recent suicide attempt. Our results highlight the importance of specific and individualized aftercare programs of sufficient duration for suicide attempters with AUD. In this context, besides suicide prevention and aftercare programs that usually focus on depression [28], the careful assessment and appropriate treatment for underlying AUD among suicide attempters should be considered.