Over-the-counter products for insomnia in adults: a scoping review of randomised controlled trials

Background: Insomnia is highly prevalent and poses significant personal and socio-economic challenges. While the National Institute for Health and Care Excellence (NICE) recommendations define possible medical approaches, over-the-counter products are commonly used to self-manage insomnia symptoms. This scoping review aims to determine the size and scope of the evidence-base regarding the effectiveness and safety of over-the-counter products for insomnia symptoms in adults.

Methods: The electronic databases of CENTRAL, MEDLINE, EMBASE, PsycINFO, and AMED were searched from inception to December 19th, 2022, for all randomised controlled trials evaluating over-the-counter products compared to placebo, in adults aged 18-65 with insomnia symptoms. Results were synthesised descriptively.

Results: 51 randomised controlled trials were included, evaluating herbal products (n=34), dietary supplements (n=15), herbal-dietary combinations (n=4), and over-the-counter medicines (n=2). Sample sizes ranged between 10 and 405 participants. Eleven studies were conducted in participants with co-morbidities. Interventions were most frequently given as monotherapy and compared against placebo. Most studies (n=41) demonstrated interventions’ positive effects on insomnia symptoms. Among the most studied products, valerian and melatonin have substantial evidence to demonstrate their effectiveness and safety. Promising products demonstrating benefits compared with prescription medication alone included: valerian; lemon balm and fennel; and valerian, hops, and passionflower. Intervention-related side effects were mostly mild and transient. No serious adverse events were reported across all studies.

Conclusions: Over-the-counter products show promising, but inconclusive findings in alleviating insomnia symptoms in adults. Future research should focus on investigating products currently used in real life, consider economic evaluations, and be evaluated in populations with co-morbidities and ethnic minorities, to better guide clinical advice.