Changes in Processing Speed, Cognitive Flexibility, and Selective Attention over a Four-Week Treatment Period in Inpatients with Moderate to Severe Depression

Abstract

Abstract. Cognitive dysfunction among individuals with depression is associated with reduced functional status, and cognitive improvement is often an important treatment goal. We compared changes in cognitive performance over four weeks among 45 inpatients with a unipolar depressive disorder completing inpatient treatment to that of 20 controls on measures of processing speed and set-shifting (Trail Making Test), as well as selective attention (Test d2). In the patients, depressive symptoms improved significantly and with a large effect over the treatment period ( d = 1.22–1.81). Among the three cognitive domains examined, the most pronounced reductions among patients compared to controls were observed in cognitive flexibility (Group effect: ηp2 = .04). The effect of Group; however, was not significant. Likewise, there were no significant improvements in cognitive flexibility over time, and changes in cognitive flexibility over the four-week period did not differ between the two groups (Group x Time interaction). Performances in selective attention and processing speed improved over the four-week period, though neither the effect of Group nor the interaction (Group x Time) was significant regarding these performances. Change in cognitive performance was not associated with changes in symptom severity (incl. remission status). Taken together, the significant improvements in selective attention and processing speed were largely attributable to practice effects. Our findings lend further support to the notion that cognitive flexibility, selective attention, and processing speed are independent of improvements in depressive symptoms. This study underscores the importance of including comparison groups to control for practice effects when examining cognitive change, and providing treatments specifically aimed at improving cognitive symptoms.