The American Foundation for Suicide Prevention reports that the suicide rate in the United States has steadily risen over the last decade. In 2022, 14.21 suicides were reported per 100,000, with far more suicide attempts (approximately 1.6 million) in the same year (American Foundation for Suicide Prevention, 2024). Whether universal morality should prevent suicide or respect it as an individual choice is a deep philosophical debate. However, considering that what most suicide attempters want is eliminating not themselves but the emotional distress they are experiencing (Rosenberg, 1999), mental health professionals, whose main job is to care and treat people's psychological distress and lead them to live better lives, have a duty to prevent their patients or clients from ending their life.

Suicide is not committed suddenly; rather, according to the integrated motivational-volitional model of suicidal behavior, it typically develops through a series of processes (O'Connor and Kirtley, 2018). The first phase is the pre-motivational phase, in which vulnerability factors (diatheses and environmental context) are combined with stressful life events and create the conditions for the emergence of suicidal ideation. The second phase is the motivational phase, during which feelings of defeat or humiliation lead to a sense of entrapment. This is influenced by the threat to self-moderators (e.g., social problem-solving, coping strategies), and feelings of entrapment subsequently give rise to suicidal ideation and intent, which are moderated by motivational moderators (e.g., thwarted belongingness, perceived burdensomeness). The third phase is the volitional phase, where suicidal ideation translates into suicidal behavior, a process moderated by volitional factors such as access to means or exposure to suicide. Throughout this process, suicidal behavior follows suicidal ideation. Therefore, to effectively prevent suicide, it is crucial to predict suicidal ideation in advance and implement appropriate interventions.

Numerous risk factors influencing suicidal ideation have been identified, and one of them is the presence of mood disorders, such as bipolar and depressive disorders. The suicide risk of patients with bipolar disorder is 20–30 times higher than that of the general population, whereas that of patients with major depressive disorder is 17 times higher than that of the general population (American Psychiatric Association, 2022). Therefore, it is necessary to focus closely on and monitor the suicide risk in patients with mood disorders. However, the frequency and severity of suicidal ideation differ among patients with mood disorders. To identify patients with mood disorders who are at higher risk for frequent and severe suicidal ideation, other risk factors for suicide, aside from the presence of a mood disorder, should be considered.

Recently, several studies have assessed the relationship between affective temperaments and suicidal ideation. The Temperament Evaluation of Memphis, Pisa, Paris and San Diego-Autoquestionnaire (TEMPS-A) is a self-report questionnaire for evaluating affective temperament by classifying it into anxious, cyclothymic, depressive, hyperthymic, and irritable domains (Akiskal et al., 2005). Several studies have confirmed the effectiveness of the TEMPS-A for predicting the level of suicidal ideation in different populations, including patients with mood disorders (Luciano et al., 2023), patients with blepharospasm (Berardelli et al., 2021), and adult patients with attention-deficit/hyperactivity disorder (Giupponi et al., 2020). A meta-analysis found that highly anxious, cyclothymic, depressive, and irritable temperaments are risk factors for suicidal ideation, whereas a highly hyperthymic temperament is a protective factor against suicidal ideation (Vázquez et al., 2018). However, because most previous studies analyzed data with the assumption that each affective temperament has an independent effect on suicidal ideation, their conclusion may be limited by the lack of consideration of the possible interaction effects of two or more affective temperaments on suicidal ideation.

The current study aimed to find the representative types of TEMPS-A profiles observed in actual clinical practice using latent profile analysis (LPA) and verify the relationship between TEMPS-A profiles and severity of suicidal ideation. Since LPA is close to a data-driven analytical method, it is well-suited for estimating TEMPS-A profiles based on actual clinical data, particularly in the current context where hypothesizing specific types of TEMPS-A profiles is not feasible. Through this research, we intend to identify the predictability of affective temperaments assessed by TEMPS-A for the severity of suicidal ideation in patients with mood disorders and suggest the utility of TEMPS-A in predicting and preparing for patients’ suicidal ideation in advance.