This study examined the interaction of cognitive style (as assessed self-report and information-processing battery) and stressful life events in predicting the clinician-rated depressive and manic symptomatology of participants with Research Diagnostic Criteria lifetime diagnoses of bipolar disorder (n = 49), unipolar depression (n = 97), or no lifetime diagnosis (n = 23). Bipolar and unipolar participants' attributional styles, dysfunctional attitudes, and negative self-referent information processing as assessed at Time 1 interacted significantly with the number of negative life events that occurred between Times 1 and 2 to predict increases in depressive symptoms from Time 1 to Time 2. Within the bipolar group, participants' Time 1 attributional styles and dysfunctional attitudes interacted significantly, and their self-referent information processing interacted marginally, with intervening life events to predict increases in manic symptoms from Time 1 to Time 2. These findings provide support for the applicability of cognitive vulnerability–stress theories of depression to bipolar spectrum disorders.

The role of cognitive processes in the phenomenology, onset, course, and treatment of unipolar depression has been the subject of fruitful scientific investigation over the past two decades. Both Beck's (1967) theory and the hopelessness theory (Abramson, Metalsky, & Alloy, 1989; Alloy, Abramson, Metalsky, & Hartlage, 1988) are cognitive vulnerability–stress models of depression that view maladaptive cognitive patterns as vulnerabilities that heighten the risk both for becoming depressed and for experiencing increased severity and duration of depression when confronted with stressful life events. Whereas these theories have expanded our understanding of unipolar depression (e.g., Abramson, Alloy, & Metalsky, 1995; Alloy, Abramson, et al., 1999; Haaga, Dyck, & Ernst, 1991), little research has been done on the role of cognitive processes in the bipolar mood...