Anxiety and depression affect performance on the symbol digit modalities test over time in MS and other immune disorders.

BACKGROUND

Longitudinal studies assessing depression and anxiety effects on cognition in multiple sclerosis (MS) are limited.

OBJECTIVE

We tested whether within-person fluctuations in symptoms of depression or anxiety over time affect cognition in persons with MS, inflammatory bowel disease (IBD), rheumatoid arthritis (RA), and a lifetime history of depression/anxiety disorders (DEP/ANX) but without an immune-mediated inflammatory diseases (IMID).

METHODS

We followed participants (MS: 255, IBD: 247, RA: 154, and DEP/ANX: 306) for 3 years. Annually, they completed the hospital anxiety and depression scale (HADS) and cognitive tests including the symbol digit modalities test (SDMT). We evaluated associations of elevated symptoms (scores ⩾ 11) of anxiety (HADS-A) and depression (HADS-D) with SDMT z-scores using multivariable linear models-estimating between-person and within-person effects.

RESULTS

Participants with MS performed worse on the SDMT than participants in the DEP/ANX cohort (β = -0.68; 95% CI: -0.88, -0.48). Participants with elevated HADS-A scores performed worse on the SDMT than those without elevated scores (β = -0.43; 95% CI: -0.65, -0.21), particularly those with RA. Time-varying within-person elevations in depressive symptoms were associated with worse SDMT performance (β = -0.12; 95% CI: -0.21, -0.021).

CONCLUSIONS

Across persons, elevated symptoms of anxiety adversely affected information processing. Elevated symptoms of depression within-persons over time were associated with declines in information processing speed.