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

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 ( = 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 ( = 0.001, η = 0.08; worsened mood with worsened executive control; improved mood with improved executive control), even when adjusting for cognitive speed ( = 0.002, η = 0.08). There were no links to cognitive speed ( = 0.826) or memory ( = 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.