This study assesses the safety, tolerability, and efficacy of suvorexant in multiple sclerosis patients. Enrolled subjects will receive 2 weeks of treatment during treatment period 1 with either suvorexant or matching placebo (1:1). After treatment period 1, subjects will undergo a washout period of 1 week then 2 weeks of the alternate treatment (either suvorexant or placebo). The primary hypothesis is that suvorexant will provide greater improvement in sleep, as measured by symptom rating scales, compared to placebo.