Subsyndromal Depressive Symptoms in Bipolar Disorder: Associations with Functioning, Internalized Stigma,...

Backgrounds/Objectives: Subsyndromal depressive symptoms are common during inter-episode periods in bipolar disorder and have been associated with functional impairment. This study aimed to examine their clinical and psychosocial correlates across multiple domains and to evaluate depressive symptom severity from both categorical and dimensional perspectives. Methods: This cross-sectional study included 133 outpatients with bipolar I disorder who had experienced no syndromal mood episode during the preceding six months. Patients were classified as having subsyndromal depressive symptoms (n = 61; HDRS 8-14 and YMRS < 8) or as euthymic (n = 72; HDRS < 8 and YMRS < 8). Clinical characteristics, functioning, impulsivity, internalized stigma, and anxiety were assessed. Results: The subsyndromal depressive group had higher total and depressive episode counts and more frequent histories of antidepressant-induced manic switch and suicide attempt than the euthymic group (all p < 0.05). They also showed lower functioning and higher impulsivity, internalized stigma, and anxiety (all p < 0.05). Within the subsyndromal depressive group, depressive symptom severity was associated with the number of depressive episodes and specific domains of functioning, impulsivity, internalized stigma, and anxiety. Conclusions: Subsyndromal depressive symptoms were associated with clinically relevant differences across multiple clinical and psychosocial domains during inter-episode periods in bipolar I disorder. The associations observed across specific domains also support considering depressive symptom severity dimensionally alongside categorical assessment.