Circulating Growth Factors and Cytokines Correlate with Temperament and Character Dimensions in Adolescents with Mood Disorders.

Background/Objectives: The incidence of mood disorders in adolescents is increasing. Bipolar disorder is often misdiagnosed in the early stages of the disease due to the prevalence of depressive symptoms, while manic episodes occur later. Identifying predictors of diagnosis conversion could facilitate timely and appropriate treatment. Our study aimed to find correlations of selected peripheral protein levels with temperament and character traits in adolescents diagnosed with major depressive disorder and bipolar disorder. Methods: A group of adolescents and young adults diagnosed with major depressive disorder (MDD, n = 50) or bipolar disorder (BD, n = 24) was enrolled in the study during the exacerbation of symptoms and followed up over two years. Diagnosis conversion from MDD to BD was monitored. The Temperament and Character Inventory was applied, and BDNF, proBDNF, EGF, MIF, SCF, S100B, TNF-alpha, and IL-8 serum levels were measured. Spearman's rank correlation analysis was conducted. Results: We found different patterns of correlations in MDD (TNF-alpha, IL-8, EGF, S100B with reward-dependence, self-directedness, and empathy) and BD (BDNF and EGF with persistence novelty-seeking and self-transcendence). Significant correlations were found in a group with diagnosis conversion. Conclusions: The findings of our study have the potential to significantly impact our understanding and treatment of mood disorders. Correlations obtained in the subgroup with diagnosis conversion may contribute to the development of prognostic markers in the future. Evaluating temperament and character traits alongside established biomarkers may offer a valuable method for predicting the conversion of mood disorders in adolescents, facilitating early and effective pharmacotherapy.