Inter-episode affective intensity and instability: Predictors of depression and functional impairment in bipolar disorder

• We examine the influence of inter-episode affect on symptoms in bipolar disorder.
• Affect was measured daily for 7 weeks while participants remained inter-episode.
• More intense inter-episode negative and positive affect predicts depression.
• More unstable negative and positive affect predicts impaired functioning.
• Daily affect monitoring may aid earlier detection of symptoms in bipolar disorder.

Background and objectivesDysregulated affect is a hallmark feature of acute episodes of bipolar disorder (BD) and persists during inter-episode periods. Its contribution to course of illness is not yet known. The present report examines the prospective influence of inter-episode affect dysregulation on symptoms and functional impairment in BD.MethodsTwenty-seven participants diagnosed with inter-episode bipolar I disorder completed daily measures of negative and positive affect for 49 days (±8 days) while they remained inter-episode. One month following this daily assessment period, symptom severity interviews and a measure of functional impairment were administered by telephone.ResultsMore intense negative affect and positive affect during the inter-episode period were associated with higher depressive, but not manic, symptoms at the one-month follow-up assessment. More intense and unstable negative affect, and more unstable positive affect, during the inter-episode period were associated with greater impairment in home and work functioning at the follow-up assessment. All associations remained significant after controlling for concurrent symptom levels.LimitationsThe findings need to be confirmed in larger samples with longer follow-up periods. A more comprehensive assessment of functional impairment is also warranted.ConclusionsThe findings suggest that a persistent affective dysregulation between episodes of BD may be an important predictor of depression and functional impairment. Monitoring daily affect during inter-episode periods could allow for a more timely application of interventions that aim to prevent or reduce depressive symptoms and improve functioning for individuals with BD.