Impact of Suvorexant on Sympathetic Nerve Activity and Baroreflex Function in Chronic Insomnia

Inclusion Criteria: * Minimum 3 months of clinically diagnosed insomnia * Body mass index ≤35 kg/m2 * Insomnia Severity Index (ISI) \> 7 arbitrary units (i.e., mild-to-severe insomnia) * Pre-menopausal women must have regular menstrual cycles (\~26-30 day cycles) and will be scheduled for microneurography 2-7 days after menstruation to consistently test during the early follicular phase (or low-hormone phase in women on contraceptives) Exclusion Criteria: * Current or prior treatment of Suvorexant. * Obstructive sleep apnea defined as an apnea-hypopnea index \> 30 using an FDA approved home sleep apnea screening devices as used in routine clinical practice. * Participants without evidence of clinically significant obstructive sleep apnea on the screening test will undergo an overnight in-laboratory polysomnography to confirm absence of sleep apnea (apnea-hypopnea index of ≥ 30 episodes per hour) and to exclude other sleep disorders (e.g. periodic limb movement arousal index of ≥ 5 episodes per hour) * Circadian rhythm sleep disorders * History of meeting DSM-V criteria of major psychiatric disorder * Have been clinically-diagnosed with diabetes, cardiovascular disease, or any other unstable or serious medical condition. * Current, or use within past month, of psychoactive (other than stable treatment with antidepressant or antianxiety), hypnotic, stimulant or analgesic medication (except occasional non-narcotic analgesics) * Shift work or other types of self-imposed irregular sleep schedules * Habitual smoking (6 or more cigarettes per week) * Habitual alcohol consumption (more than 2 alcoholic drinks per day) * Breastfeeding or pregnancy