Response to lithium maintenance treatment in bipolar disorders: comparison of women and men

Possible sex differences in responses to mood-stabilizing treatment remain poorly defined. Since women with bipolar disorder reportedly have more features that may predict a poor prognosis (depression and rapid cycling), we tested the hypothesis that women respond less well to lithium maintenance treatment.

Clinical characteristics of 360 women and men with DSM-IV bipolar I or II disorder were compared before and during clinical lithium maintenance monotherapy in a mood disorders clinic by preliminary bivariate comparisons, multivariate analysis, and survival analysis of time stable during treatment.

Women (n = 229) versus men (n = 131) were: more likely to have type II disorder (1.6 times), 3.2 years older at illness onset, more often depressed-before-manic (1.4 times), considered unipolar depressive 1.9 years longer and started maintenance treatment 5.5 years later. However, women differed little from men before treatment in overall morbidity, average episode frequency and risk of suicide attempts. Contrary to prediction, women showed non-significantly superior responses to lithium treatment, and a significant 60% longer median time before a first recurrence during treatment, despite 7% lower average serum lithium concentrations.

Women were diagnosed as bipolar later than men with corresponding delay of lithium maintenance treatment that proved to be at least as effective as in men.