Anxiety Trait as a Potential Endophenotype in First-Degree Relatives of Bipolar Disorder Type I Patients

Background: Primary care providers are increasingly using screening programs to identify patients at risk of mental disorders. Early diagnosis of bipolar disorder type I (BDI) is essential for a better outcome. Endophenotypes are an important subtype of biomarkers. Furthermore, previous studies show anxiety trait as a possible BDI endophenotype, but there is a lack of replication. Objective: Our study evaluates the presence of anxiety trait and bipolarity risk in bipolar disorder type I first-degree relatives (FDR). Methods: We evaluated 219 participants (119 healthy controls, 68 healthy FDR and 32 affective unipolar FDR), including sociodemographic data, psychiatric history, Spielberg’s State and Trait Anxiety Inventory (STAI), General Health Questionnaire, Beck Depression Inventory, and Mood Disorder Questionnaire (MDQ) scores as a measure of bipolarity risk. Results: In our sample, affective unipolar BDI’s first-degree relatives showed the highest scores in STAI anxiety trait compared to healthy controls and BDI’s healthy first-degree relatives. STAI-Trait only correlated significantly with bipolarity risk (MDQ) in the unipolar affective first-degree relatives subgroup. Conclusions: Although further investigation is warranted, trait anxiety is a potential endophenotype for BDI. It exhibits high heritability and confers an increased lifetime risk for unipolar affective disorder and a predisposition toward bipolarity.