• bipolar disorder;
  • lithium efficacy;
  • prophylaxis

Objectives: The aim of the study was to assess the prophylactic effect of long-term lithium administration in patients with bipolar mood disorders entering treatment in the 1970s and 1980s at the outpatient clinic of the Department of Psychiatry, University of Medical Sciences, Poznan, Poland. Methods: The clinical characteristics of two groups of patients before and during lithium therapy were compared, namely, the 60 bipolar patients who entered lithium prophylaxis in the 1970s and 49 patients who entered in the 1980s. Both groups received the drug over a 10-year period. Results: The patients who entered lithium in the 1970s had fewer previous episodes of depression and more of mania than the patients who entered the therapy in the 1980s, although the total number of affective episodes was similar in both groups. The overall prophylactic efficacy of lithium over a 10-year period of administration was similar in both groups, except for a trend towards a greater number of depressive episodes in the first year of lithium prophylaxis in the 1980s group. The excellent lithium responders constituted 35% of the 1970s patients and 27% of those in the 1980s group. The 1970s patients were maintained on a higher level of serum lithium compared to the patients in the 1980s group and had more lithium-induced side effects. Conclusions: A decrease in lithium prophylactic efficacy in consecutive decades was not observed. Small differences between the bipolar patients entering lithium therapy in the 2 decades were observed in terms of the previous history of illness and during the course of lithium administration.