Insomnia Symptoms, Subjective Appraisals, and Fatigue: A Multiple Mediation Model.

Mediation analyses revealed a significant association between insomnia symptom severity and the cognitive and physical domains of fatigue. Fatigue catastrophizing was the only significant mediator, accounting for 25% of the variance in the relationship between insomnia symptoms and the cognitive fatigue. However, fatigue catastrophizing did not significantly mediate the relationship between insomnia symptoms and physical fatigue, indicating physical and cognitive fatigue may reflect distinct processes in fatigue expression in those with MS.