When German psychiatrist Emil Kraepelin (1856-1926) studied emotions in patients with affective disorders, he identified four temperaments: the depressive (DT), the hyperthymic (HT), the irritable (IT), and the cyclothymic (CT). Subsequent researchers later identified an anxious temperament (AT).
“The notion that temperaments can be useful in predicting bipolar disorders sparked a plethora of research,” wrote Elie G. Karam, MD, of Saint George Hospital, Beirut, and colleagues. In particular, the cyclothymic (CT) and irritable (IT) temperament types have been targeted in studies of patients with bipolar disorders, but previous studies of temperament and bipolar have been limited by methodological issues, they said.
In a study published in European Psychiatry, the researchers reviewed data from 1,723 consecutive adult outpatients who presented to a university-based mental health clinic with various symptoms between January 2014 and September 2019.
Patients were assessed using the Hypomania Checklist-32 (HCL-32) and the Temperament Evaluation of Memphis, Pisa, Paris, and San Diego-Auto-questionnaire (TEMPS-A), then were diagnosed by psychiatrists using DSM-5 criteria. Patients with any bipolar types as defined by the DSM-5 underwent simple and multiple binary logistic regression analyses. The analysis included continuous scores and categorical normalized z-scores.
A total of 369 patients had confirmed DSM-5 diagnosis of bipolar disorder (52 with type I, 176 with type II, 102 with other specified bipolar and related disorder, and 39 with substance- or medication-induced bipolar disorder. The mean age of the participants was 38 years, and 54% were female.
In a bivariate analysis, all continuous temperament scores were significant predictors of bipolar disorder; all except AT remained significant in multivariate analysis. Increasing scores of IT, CT, and HT were associated with bipolar disorder, but increasing scores of DT were reflective of lower chance of bipolar disorder, the researchers noted.
In multivariate analysis of categorical normalized z-scores, IT and CT were significant predictors of bipolar disorder. At the highest point, CT was the stronger predictor, compared with IT (odds ratio, 3.84 vs. 2.55); having a higher DT score significantly reduced the odds of bipolar disorder (OR, 0.50).
However, “after adjusting for the presence of all temperaments as well as age and gender, only IT remained a significant predictor of patients with bipolar I disorder with adjusted OR of 1.19,” the researchers wrote.
“Correlations among temperaments were solid whether looking at patients with bipolarity or not, further emphasizing the necessity of controlling for them,” the researchers wrote in their discussion.
The findings were limited by several factors including the lack of structured interviews, the use of an outpatient-only sample, and the small number of bipolar I patients, the researchers noted.
However, the result suggest that IT can serve as a predictor of bipolar I and bipolar II disorders they said. Given the underdiagnosis of bipolar disorder in many studies, the incorporation of temperaments into the assessment of patients and research participants alike is likely to help us detect the presence of bipolarity more readily and quite importantly help us in our quest to understand their genesis,” they concluded.
The study was supported in part by anonymous private unrestricted donations to IDRAAC, Lebanon, and by Eli Lilly. The researchers had no financial conflicts to disclose.