Depression symptoms and cognition in multiple sclerosis: Longitudinal evidence of a specific link to executive control

Abstract

Background: Depression symptoms are prevalent in multiple sclerosis (MS) and associated with poorer cognition in cross-sectional studies; it is unknown whether changes in depression symptoms track with cognitive changes longitudinally. Objective: Investigate whether changes in depression symptoms correspond with cognitive changes over time in MS, and identify specific cognitive functions related to depression symptoms. Method: Persons with early relapse-onset MS ( n = 165) completed a depression questionnaire (Beck Depression Inventory FastScreen) and tests of cognitive speed, executive control, and memory at baseline and 3-year follow-up. One-way ANOVAs assessed differences in cognitive change across participants with worsened, stable, or improved depression symptoms from baseline to year 3. Results: Change in depression symptoms was related to change in executive control ( p = 0.001, ηp2 = 0.08; worsened mood with worsened executive control; improved mood with improved executive control), even when adjusting for cognitive speed ( p = 0.002, ηp2 = 0.08). There were no links to cognitive speed ( p = 0.826) or memory ( p = 0.243). Regarding individual depression symptoms, executive control was related to loss of pleasure and suicidal thoughts. Conclusions: Executive control tracks with depression symptoms, raising hope that management of mood may improve executive control. The specific link between executive control and anhedonia implicates dysfunctional reward processing as a key component of MS depression.