To the best of our knowledge, this is the first study exploring the associations of temperament, depressive symptoms and suicide risk among first-episode neuroleptic-naïve MDD patients. In these subjects, we obtained the following: (1) suicide rate; (2) temperament trait differences from healthy controls; (3) cyclothymic and dysthymic temperament, as well as sex, age, and severe depression, were independent risk factors for suicide risk; and (4) the compound predictor for suicide risk in first-episode neuroleptic-naïve MDD.
Many studies have shown that depressive episode frequency is closely related to suicidal risk[8, 28, 29]. A higher episode frequency means a higher suicide rate. In this study, we found that the suicide rate of first-episode neuroleptic-naïve MDD was as high as 47.62%, close to previous studies of major depressive disorder from 47–69%[30–32], meaning that nearly half of the depressive patients had suicidal ideation or attempted suicide during their first major depressive episode.
Approximately 20% of the general population has a certain type of emotional temperament. Generally, females are prone to be dysthymic, cyclothymic and anxious temperament, while males are prone to be hyperthymic and irritable temperament; some specific affective temperaments have a higher suicidal risk. In this study, the direction of temperament in healthy controls was hyperthymic > irritable > anxious >cyclothymic >dysthymic, and in MDD, it was dysthymic > cyclothymic > anxious > irritable > hyperthymic, which is evidence that more females than males suffer from depression. This study tried to identify suicide risk factors for temperament in first-episode depressive patients. Compared with the healthy controls, the first-episode MDD patients scored significantly different on dysthymic, cyclothymic, anxious and irritable temperaments, and the significant difference direction was dysthymic > cyclothymic > anxious > irritable.
We compared the temperament differences between suicidal and nonsuicidal risk in depressive patients. As expected, cyclothymic and dysthymic temperaments were associated with a greater risk of suicide. The five factors significantly and independently differentiated patients with versus without suicidal risk based on multivariable logistic regression modeling: female sex, current age, dysthymic and cyclothymic temperament and higher HAMD score. The compound predictor of the five sets a model of high suicide risk. The final factors/features of suicide-risk patients were the same as the clinical impressions, and young females with severe major depressive disorder always complained of hopelessness. Their characteristics may include cyclothymia or dysthymia before the depressive episode. People with cyclothymic temperament traits show instability in mood, thoughts, and behaviors, while mood instability usually leads to suicidal behavior, and quickly changing mood stations enhance suicidal ideation and attempts. Depressive patients with cyclothymic temperament traits are probably developing bipolar disorder and high rates of suicide and hospitalization[20, 34], which might be the final outcome for cyclothymic temperament trait depressive disorder patients.
Many previous studies have examined the demographic characteristics of suicide risk factors in depressive disorder patients. As expected, the onset age was strongly associated with suicide, which is also supported by other studies[27, 35]. Early onset age (especially <18 years) of depression is associated with an increasing rate of converting to bipolar disorder, which is a high risk factor for suicide[20, 37]. Subjects of this study were people with a current age over 18 years, and the mean illness duration was 6-6.5 months; we did not obtain the suicide rate of younger adolescents, which still needs further research. Other demographic suicide risk factors in MDD included female sex (71.25%) and unmarried status (76.25%), in accordance with previous observations[20, 38]. We found that a greater suicide risk was more associated with female sex, which was also confirmed in other studies[17, 39]. However, men may have more violent suicide attempts than women, and lethal action makes their suicide death rate higher than in women, which also needs further study. Our study showed that unmarried or unemployed persons are a population significantly suffering from depression, and unmarried people have significantly higher instances of thoughts or actions of suicide.
In our study, first-episode depression was detected in the subjects by the HAMD. As the disease progresses, the final diagnosis might be unipolar disorder, bipolar disorder or other mental diseases accompanied by affective symptoms. We found that HAMD scores that removed the 3rd (suicide) item could still predict suicidal risk in major depressive disorders. This means that the total HAMD-17 score, in addition to the 3rd (suicide) item, is closely linked to suicide risk[40, 41]. Particularly of note, the standardized HAMD scale predicting suicide may result in approximately 30% false positives, which is inevitable.
Serotonin is a neurotransmitter involved in many brain and body functions. Impaired serotonergic function is involved in the development of suicide behavior and was proven decades ago. Some studies on genes showed that depression and suicide were at the same gene locus[6, 44–46], other than a causal relationship. They found that the S allele in the serotonin transporter-linked polymorphic region (5-HTTLPR) may associate with affective temperament, especially cyclothymic temperament. Sarmiento-Hernández’s study showed that the S-allele and the SS genotypes of 5-HTTLPR were associated with suicide attempts. They provide a theoretical basis for the relationship between cyclothymic temperament and suicide. If the suicide risk and temperament are genetic phenotypes and share the same locus, is interference difficult? Other studies have shown that affective temperaments may change to some degree, and people could exhibit one type of character trait during puberty and deviate when they grow up. They provide the basis that temperament is changeable throughout a person’s life. Japanese researcher Inoue studied the influence of ambient temperature on temperament, which makes us believe that the final outcome could be intervened.