Background. Depression is usually the predominant affective state in bipolar disorder. There are few studies, with discrepant views, examining the extent of cognitive impairment in patients with bipolar depression. To our knowledge, there are no previous studies examining decision-making ability or whether there is an affective attentional bias in bipolar depression.

Method. We ascertained 24 depressed bipolar I patients from acute psychiatric hospital wards and out-patient clinics and 26 age- and IQ-matched healthy controls. Using computerized tests we evaluated their performance on ‘neutral’ (non-emotional) cognitive tasks (i.e. memory, attention and executive function) and on novel tasks of emotional cognition (i.e. the decision-making task and the affective go/no-go task).

Results. Accuracy measures were significantly impaired on tests of visual and spatial recognition and attentional set-shifting in bipolar depression compared with age- and IQ-matched controls. The quality of decision-making was also significantly impaired in the patients. A mood-congruent attentional bias for ‘sad’ targets was not evident on the affective go/no-go task.

Conclusions. We found widespread evidence of significant cognitive impairment and impaired quality of decision-making in symptomatically severe depressed bipolar patients. This cognitive impairment may contribute to difficulties with daily living, decision-making and the ability to engage and comply with psychological and drug treatments.