Objective: To examine the relationship between number of episodes and inter-episode functioning in bipolar disorder.
Method: Sixty-four euthymic subjects with bipolar affective disorder completed the Medical Outcomes Questionnaire Short Form and the Global Assessment of Functioning Scale. Goodness-of-fit models were used to define the relation between episode number and level of function.
Results: Non-linear logarithmic and power relations best described the association between number of episodes and outcome. Number of past depressions was a stronger determinant of outcome than past manias.
Conclusion: Strategies to minimize the number of episodes experienced by patients with bipolar illness must be pursued aggressively if function is to be maintained, with particular attention given to minimizing episodes of depression.