The Influence of Predominant Polarity and Chronotype on Lithium Response in Bipolar Disorder

Aim: This study investigates the prevalence and clinical correlates of predominant polarity (PP), depressive predominant polarity (DPP), and manic predominant polarity (MPP) in patients with bipolar disorder type 1 (BD-1), as well as their association with chronotype and lithium response. Method: The present study with a cross-sectional design was conducted on 80 BD-1 patients in remission between 18-65 years of age. Data collection involved sociodemographic questionnaires and assessments using the Young Mania Rating Scale (YMRS), Hamilton Depression Rating Scale (HDRS), Biological Rhythms Interview of Assessment in Neuropsychiatry, (BRIAN) Morningness-Eveningness Questionnaire (MEQ), and the Alda Scale. DPP and MPP were defined as a lifetime ratio of ≥2:1 of either hypomanic/manic episodes or depressive episodes, respectively. Results: Participants (mean age 35.32 ± 11.39 years; 61.25% female) showed two dominant polarities: DPP (46.25%) and MPP (53.75%). No significant differences were found in treatment, illness duration, or episode number (p>0.05). However, the MPP group had significantly earlier onset age (p=0.009) and higher scores on the BRIAN, MEQ, and Alda scales (all p<0.001). Manic episodes correlated positively with BRIAN and strongly with MEQ (rs1=-0.355, rs2=-0.373). The Alda scale showed strong positive correlations with BRIAN and MEQ, and strong negative correlations with depressive episodes (rs1=-0.355, rs2=-0.373, rs3=-0.274). Conclusion: The present study demonstrates that PP and chronotype significantly influence lithium response in individuals with BD-I. The MPP group was found to have an earlier onset of the disorder and exhibit more pronounced evening characteristics. Additionally, the MPP group showed a stronger response to lithium.