Impairment in cognitive performance is an important characteristic in many psychiatric illnesses, such as Bipolar Disorder and Major Depressive Disorder. Initially, cognitive dysfunctions were considered to be present only in acute depressive episodes and to improve after symptoms recovered. Reports have described persistent cognitive deficits even after significant improvement of depressive symptoms.

We wanted to understand the dimension of cognitive impairment in unipolar and bipolar depression and also to underline the differences between cognitive profiles of patients diagnosed within the two mentioned disorders.

This review examined recent literature about unipolar and bipolar depression.

Both depressed patients presented cognitive deficits in several cognitive domains. Different aspects of attention were altered in both patients but impairment in shifting attention appeared specific to unipolar disorder while impaired sustained attention was particular for bipolar disorder. Both types of patients showed memory deficits that were associated with poor global functioning. Two recent studies described that bipolar depressed subjects were more impaired across all cognitive domains than unipolar depressed subjects on tests assessing verbal memory, verbal fluency, attention and executive functions. The most consistently deficits were displayed on measures of executive functioning – such as tasks requiring problem solving, planning, decision making – suggesting that this cognitive domain is a trait-marker for depression.

Cognitive deficits are present in both disorders during a depressive episode but they display slightly different patterns of impairment.

The authors have not supplied their declaration of competing interest.