Background. A long-standing debate concerns whether dysfunctional cognitive processes and content play a causal role in the etiology of depression or more simply represent correlates of the disorder. There has been insufficient appreciation in this debate of specific predictions afforded by cognitive theory in relation to major life stress and changes in cognition over time. In this paper we present a novel perspective for investigating the etiological relevance of cognitive factors in depression. We hypothesize that individuals who experienced a severe life event prior to the onset of major depression will exhibit greater changes in dysfunctional attitudes over the course of the episode than will individuals without a severe life event.

Method. Fifty-three participants diagnosed with major depression were assessed longitudinally, approximately 1 year apart, with state-of-the-art measures of life stress and dysfunctional attitudes.

Results. Depressed individuals with a severe life event prior to episode onset exhibited greater changes in cognitive biases over time than did depressed individuals without a prior severe event. These results were especially pronounced for individuals who no longer met diagnostic criteria for major depression at the second assessment.

Conclusions. Specific patterns of change in cognitive biases over the course of depression as a function of major life stress support the etiological relevance of cognition in major depression.