Pain Affects Depression Through Anxiety, Fatigue, and Sleep in Multiple Sclerosis

Objective: Over a quarter million individuals in the United States have multiple sclerosis (MS). Chronic pain and depression are disproportionately high in this population. The purpose of this study was to examine the relationship between chronic pain and depression in MS and to examine potentially meditational effects of anxiety, fatigue, and sleep. Method: We used cross-sectional data from self-reported instruments measuring multiple symptoms and quality of life indicators in this study. We used structural equation modeling to model direct and indirect effects of pain on depression in a sample of 1,245 community-dwelling individuals with MS. Pain interference, depression, fatigue, and sleep disturbance were modeled as latent variables with 2 to 3 indicators each. The model controlled for age, sex, disability status (Expanded Disability Status Scale), and social support. Results: A model with indirect effects of pain on depression had adequate fit and accounted for nearly 80% of the variance in depression. The effects of chronic pain on depression were almost completely mediated by fatigue, anxiety, and sleep disturbance. Higher pain was associated with greater fatigue, anxiety, and sleep disturbance, which in turn were associated with higher levels of depression. The largest mediating effect was through fatigue. Additional analyses excluded items with common content and suggested that the meditational effects observed were not attributable to content overlap across scales. Conclusion: Individuals living with MS who report high levels of chronic pain and depressive symptoms may benefit from treatment approaches that can address sleep, fatigue, and anxiety.