Does depression in multiple sclerosis mediate effects of cognitive functioning on quality of life?

Patients with multiple sclerosis (MS) are at significant risk for decreased quality of life (QoL), in part due to factors such as cognitive impairment and depression. However, objective versus subjective assessments of cognitive functioning may differentially predict QoL, and it remains unknown whether they each impact QoL through levels of depression. The aims of the present study included (1) testing the effects of cognitive impairment on MS-related QoL via depression symptoms and (2) examining whether perceived and objective cognitive functioning differentially predict QoL through depression.

Patients formally diagnosed with MS (N = 128) participated in cognitive assessment (Brief International Cognitive Assessment for Multiple Sclerosis) and completed self-report measures of perceived cognitive functioning (perceived deficits questionnaire), depression (Hospital Anxiety and Depression Scale), and MS-related QoL (functional assessment of multiple sclerosis).

Mediational hypotheses were tested by regression and structural equation modeling. As hypothesized, both perceived and objective cognitive functioning independently predicted lower QoL controlling for the effects of depression (p < 0.001). Consistent with hypotheses, depression mediated effects of both perceived (95% CI [0.31, 0.68]) and objective cognitive functioning (95% CI [0.09, 6.96]) on QoL when tested in separate models. However, when both predictors were modeled simultaneously, depression only mediated the effects of perceived (not objective) cognitive functioning (95% CI for standardized effect [0.10, 0.61]).

This study, thus, suggests the need to conceptualize different pathways by which objective and subjective cognitive impairment may shape QoL in the lives of individuals with MS.