Objectives. Biological rhythm disturbances make an etiological factor and a feature of bipolar disorder (BD). Bipolar patients are more likely to represent an evening chronotype. Lithium, hich is used in the treatment and prophylaxis of BD, favorably influences biologicalrhythms. In this study, we evaluated the lithium therapy effects on circadian rhythm in remitted bipolar patients
compared to healthy controls.
Material and methods. Fifty-four remitted BD patients (37 female and 17 male), aged 52 ± 13 years and 54 healthy control subjects (29 female and 25 male) aged 42 ± 14 years were studied. Half of the patients were treated with lithium. We assessed each of the subjects using the Composite Scale of Morningness (CSM).
Results. Bipolar patients taking mood-stabilizing drugs other than lithium – BP Li (–) achieved 29.78 ± 9.81 points in the Composite Scale of Morningness, patients treated with lithium carbonate – BP Li (+) gained 35.67 ± 7.67 and average score of the control group was 35.04 ± 8.40. The greatest difference was obtained for "the time of best performance" (8th item of CSM), where BP Li (–) indicated significantly later hours during the day compared to BP Li (+) and healthy controls.
Conclusions. The conducted study has many limitations, however, allowed to observe a significant effect of lithium on the circadian rhythm in euthymic bipolar patients. Lithium-treated patients showed more tendency to morningness compared from BP Li (–). Biological rhythm disturbances and worse quality of life are more common in people with an evening chronotype. The effect of lithium on biological rhythms can make a significant element of its mood-stabilizing action in BD.