The relationship between depressive symptoms, hypomanic symptoms, mood, and category learning.

Participants completed several self-assessments that measured depressive symptoms, hypomania, and mood. They were then asked to learn either a set of rule-based categories or a set of non-rule-based categories. Correlational analyses suggested that participants with high levels of self-reported depression were impaired on complex rule learning. In contrast, performance on a rule-based learning task was found to be improved by high levels of current positive mood. Multiple linear regression analyses further revealed that, when the variance due to other constructs was removed, the relationship between depressive symptoms and rule-based performance disappeared while the relationship between positive mood and rule-based performance remained significant. These findings suggest that positive mood is related to enhanced rule learning abilities. Neither level of depression nor positive mood were found to be related to performance on categories that could be learned via associative processes. This dissociation provides evidence for a dual systems approach to categorization. These findings also suggest that executive functioning impairments observed among individuals with depression may be specifically related to a lack of positive mood rather than overall depressive symptoms, per se.