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

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Abstract
Aims: 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 (BD) type 1, as well as their association with chronotype and lithium response. Method: Eighty patients aged 18-65, in remission from BD type 1, participated in this cross-sectional study. In addition to sociodemographic and clinical data, remission status, lithium response levels, and chronotype were evaluated using the Young Mania Rating Scale, Hamilton Depression Rating Scale, Biological Rhythms Interview of Assessment in Neuropsychiatry, Morningness-Eveningness Questionnaire, and Alda Scale. DPP and MPP were defined as a lifetime ratio of ≥2:1 of either hypomanic/manic episodes or depressive episodes, respectively. Results: The mean age of participants was 35.32 ± 11.39 years, with 61.25% being female (n=49). The dominant polarities were 46.25% (n=37) DPP and 53.75% (n=43) MPP. No significant differences were found between the two groups in terms of treatment types, total duration of illness, or total episode number (p>0.05). However, the onset age of the disorder was significantly earlier in the MPP group (p=0.009). This group also had significantly higher scores on the BRIAN, MEQ, and Alda Scale (t=-7.183, p=0.00; t=-3.968, p=0.00; t=-6.971, p=0.00, respectively). A weak positive correlation was found between manic episodes and BRIAN, while a strong positive correlation was observed with MEQ (respectively rs1=-0.355, rs2=-0.373). Strong positive correlations were noted between the Alda Scale and both BRIAN and MEQ, alongside strong negative correlations with the total number of depressive episodes (respectively rs1=-0.355, rs2=-0.373, rs3=-0.274). Conclusion: This cross-sectional 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. These findings suggest that lithium may have a greater effect on individuals with MPP and evening chronotype and highlight the need for validation through larger sample sizes and longitudinal studies

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