Cognitive deficits in the remitted state of unipolar depressive disorder.

Background: Patients with unipolar depressive disorder may present with cognitive deficits in the remitted state, and the aim of the present study was to investigate whether cognitive deficits within specific cognitive domains are present.
Method: Via the Danish registers (Civil Person Register, Danish Psychiatric Register) we identified individuals between 40 and 80 years of age with a diagnosis of unipolar disorder at their first discharge from a psychiatric hospital, and a gender- and age-matched control group. Particular emphasis was placed on assuring that patients were in a remitted state. Cognitive function was assessed with a broad range of neuropsychological tests.
Results: A total of 88 patients and 50 controls were included in the study. In multiple linear regression analyses with simultaneous adjustment for age, gender, education level, premorbid IQ, and residual depressive symptoms, a diagnosis of unipolar disorder predicted lower performance on the Trail Making Test, the Symbol Digit Modalities Test, and on the Stroop test.
Conclusion: Cognitive deficits are present in patients with unipolar disorder in the remitted state. The deficits seem to reside more within the cognitive domain of attention than within other domains, and may be characterized by impairment of processing speed and cognitive flexibility.