Sleep & Circadian Health
CBT-I outperforms every sleep medication in head-to-head trials. In head-to-head trials, CBT-I outperformed sleep medication, which is why behavioral treatment is graded ahead of supplements here.
Harmsen et al. (Cell Metab, 2026; PMID PubMed ID: the permanent number the US National Library of Medicine gives a published paper. Each one links to that paper's record on PubMed. 41418772) ran a randomized crossover A trial design in which each participant receives both the treatment and the comparison, one after the other, and serves as their own control. in 13 adults with type 2 diabetes: 4.5 days of daylight through office windows kept glucose in the normal range for longer than constant artificial light, and shifted metabolism toward fat burning. Two large UK Biobank analyses add observational Research that watches what people already do rather than assigning a treatment. It can show that two things travel together, not that one causes the other. context: brighter days and darker nights went with lower mortality across 88,905 people wearing light sensors (Windred et al., PNAS, 2024; PMID 39405349), and each daily hour outdoors in daylight went with fewer insomnia symptoms and better mood (Burns et al., J Affect Disord, 2021; PMID 34488088). The trial is small and short and measures glucose, not disease, so daylight carries no grade.PMID 41418772 PMID 39405349 PMID 34488088
Every change to a letter on this site is dated and published. The full evidence log →
The letters on this page
Seven interventions on this page. Every one carries a letter.
- •Benzodiazepines and Z-drugs (zolpidem, eszopiclone) alter sleep architecture and can cause rebound insomnia after regular use. Stopping abruptly carries its own risks, and tapering is a decision for your physician.
- •Some beta-blockers can reduce nocturnal melatonin secretion and may contribute to sleep disturbance.
- •Many SSRIs and SNRIs alter sleep architecture and can suppress REM sleep. New or worsening sleep problems are a question for your physician.
- •Stimulants including amphetamine salts (Adderall), modafinil and high-dose caffeine can delay sleep onset and reduce sleep duration, especially when taken later in the day. Timing and dose are a decision for your physician.
- •Fluvoxamine can markedly increase melatonin exposure; ciprofloxacin and oral contraceptives can also raise levels. Melatonin can add to sedation from benzodiazepines, other sedatives and alcohol.
Meta-analysis A study that pools the numbers from several trials into one combined estimate. of 20 randomized trials against inactive comparators: sleep onset latency improved by 19 minutes and sleep efficiency by 9.9 percent, sustained at follow-up. No head-to-head comparison against sleep medication was made. Available via Sleepio, Somryst, or a trained therapist.
Ferracioli-Oda et al. (PLoS One 2013; PMID 23691095) pooled 19 randomized placebo-controlled trials, 1,683 adults and children with primary sleep disorders: melatonin shortened sleep onset by about 7 minutes, lengthened total sleep by about 8 minutes and modestly improved sleep quality. Trials using higher doses and running longer found larger effects on sleep onset and total sleep. The low-dose 0.5 to 1 mg protocol is graded separately, at C.
Sleep quality RCT in older adults. Muscle relaxation and GABA modulation contribute to sleep onset. Take in the evening with or without food.
Bannai et al. (Front Neurol 2012; PMID 22529837): 3 g before bed in healthy volunteers under experimental sleep restriction reduced next-day fatigue and improved psychomotor vigilance. Hypothermia mechanism: glycine lowers core body temperature, which facilitates sleep onset. The widely quoted Yamadera 2007 glycine study appeared in a journal PubMed does not index, so it carries no identifier and is not used here.
Cortisol reduction and HPA axis modulation. Multiple RCTs confirm sleep onset and quality improvement. Standardized root and root-plus-leaf extracts are the most studied.
Alpha wave induction in EEG studies. Early RCT Randomized controlled trial: people are assigned to the treatment or a comparison by chance, so the groups differ only in what they received. It is the design that can show cause and effect. data for sleep quality and reduced sleep latency. Often combined with magnesium. No sedation; does not cause morning grogginess.
Endogenous melatonin precursor via tryptophan pathway. Small RCTs in older adults show modest sleep duration improvement. Montmorency variety is the most studied form.
Harmsen et al. (Cell Metab 2026; PMID 41418772): a randomized crossover in 13 adults with type 2 diabetes. Over 4.5 days of daylight through office windows, against constant artificial light, continuous glucose monitoring showed more time in the normal range and metabolism shifted toward fat burning. Small, short and measured on glucose rather than disease, so it carries no grade.
Windred et al. (PNAS 2024; PMID 39405349): 88,905 UK Biobank adults wore light sensors for a week and were followed for about 8 years. Brighter daytime light went with lower all-cause mortality and brighter night light with higher. Observational.
Burns et al. (J Affect Disord 2021; PMID 34488088): in UK Biobank, each additional daily hour outdoors in daylight went with fewer insomnia symptoms, less tiredness, easier waking and lower odds of depression. Observational.
This page is educational only. Persistent insomnia lasting more than 3 months warrants clinical evaluation to rule out sleep apnea, restless leg syndrome, and psychiatric comorbidities before starting any supplement protocol. The Drug-Nutrient Depletion tool shows whether current medications may be impairing sleep.
These statements have not been evaluated by the Food and Drug Administration. Any grade on this page describes the strength of published human trial evidence in the populations studied. It is not a recommendation for any individual and is not medical advice. Starting, stopping or changing any supplement or medication is a decision for your physician.