Phase 2 trial -- suvorexant 10 mg , 20 mg , 40 mg , 80 mg , placebo ; HS study 1 -- suvorexant 10 mg , 50 mg , placebo ; HS study 2 -- gaboxadol 15 mg , zolpidem 10 mg , placebo ; HS study 3 -- trazodone 150 mg , placebo .