Table 2. Patient, intervention, control, outcome, study design (PICOS) question and eligibility criteria.

	Inclusion criteria	Exclusion criteria
(P) Patient	Insomnia disorder (according to the DSM-5) or primary insomnia (according to the DSM-4)	Overlapping patient populations
(I) Intervention	Dual orexin receptor antagonists (DORAs)	Selective orexin receptor antagonists (SORAs)
(C) Control	Placebo or placebo and zolpidem (active control drug)	–
(O) Outcome	Efficacy outcomes: wake time after sleep onset (WASO); latency to persistent sleep (LPS); total sleep time (TST)	–
(S) Study design	Randomized controlled trials (RCTs)	Studies not written in English; crossover design.

Abbreviation: DSM, Diagnostic and Statistical Manual of Mental Disorders.