Topic
Sleep & Recovery
Quick answers
- What is it?
- This hub covers what controlled research says about sleep quality and duration — how they connect to hormone levels, metabolic health, tissue repair, and injury risk — plus what's been tested for helping people sleep, from melatonin dosing to magnesium, CBD, blue-light-blocking glasses, and the research compound DSIP.
- Why are people interested in it?
- Sleep problems are common, and people want to know whether things marketed to fix them — supplements, glasses, peptides — actually work, and whether skimping on sleep has real downstream effects on hormones, weight, and injury risk.
- What has actually been studied?
- The sources span randomized controlled trials, crossover trials, systematic reviews, and meta-analyses in populations including young men, postmenopausal women, adolescent and adult athletes, and people with insomnia, testing melatonin at various doses, magnesium, CBD (with and without THC), blue-light-filtering glasses, and the research peptide DSIP (delta sleep-inducing peptide).
- How strong is the evidence?
- The strength of the evidence varies a lot by topic: sleep's short-term effects on hormones and metabolic health are backed by multiple small but tightly controlled lab trials with consistent direction; melatonin dose-response and magnesium have supportive meta-analyses that their own authors still rate low-to-very-low certainty; CBD and blue-light-blocking glasses show mixed, inconsistent trial results; and DSIP has the thinnest evidence of the group — a handful of small, decades-old, conflicting double-blind trials, with zero trials currently registered on ClinicalTrials.gov and nothing published on it since 2009.
- What don't we know yet?
- Across these topics, it's largely unknown whether short-term lab findings translate into long-term disease or injury outcomes, whether improving sleep causally reduces injury risk, what the optimal dose or product formulation is for supplements like magnesium and CBD, and whether findings in the mostly young, male, small samples generalize to women, older adults, or the general population.
- Where can I read the original research?
- Explore the individual articles in this hub for the full study-by-study breakdown on melatonin dosing, magnesium, CBD, blue light, sleep deprivation's hormonal effects, and sleep's link to metabolic health and tissue repair, and see the DSIP peptide profile for its full human-trial history.
Sleep is the recovery tool with the largest evidence base and the least marketing. This hub covers what sleep loss does to hormones and metabolism, what the trials found for common sleep aids, and the one peptide, DSIP, that was studied for sleep decades ago and largely abandoned.
Peptides in the Evidence Index
Research on this topic
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Frequently asked
Does DSIP (delta sleep-inducing peptide) actually help people sleep?
The evidence is thin and old. The one placebo-controlled human trial (Bes et al., 1992, n=16) found DSIP produced slightly better sleep efficiency and shorter sleep latency than placebo, but the study's own authors called the effect weak and said it was "not likely to be of major therapeutic benefit." Other human data is mostly decades-old case reports and small studies that disagree with each other, and a 2006 review called the DSIP-sleep link itself "extremely poorly documented and still weak." Zero DSIP trials of any kind are currently registered on ClinicalTrials.gov.
What dose of melatonin do clinical trials actually use?
Trials have tested doses ranging from roughly 1 mg to 10 mg per night. A 2024 dose-response meta-analysis of 26 trials (1,689 observations) found melatonin's sleep-promoting effect grew with dose up to about 4 mg/day — higher than the 2 mg dose commonly used in practice — and found that timing (about 3 hours before bedtime) mattered about as much as dose. An earlier 2005 meta-analysis of 17 trials found melatonin cut sleep onset latency by about 4 minutes and extended total sleep time by about 13 minutes on average. Not every population shows a dose-response pattern: a Cochrane review of shift workers using doses from 1-10 mg found none.
Do magnesium or CBD actually help with sleep?
For magnesium, a 2021 systematic review pooling 3 trials in 151 older adults found it reduced sleep onset latency by about 17 minutes versus placebo, and a 2012 trial in 46 elderly adults found improvements in insomnia severity and sleep efficiency — but total sleep time didn't significantly improve in either, and reviewers rated the evidence low-to-very-low quality; several other trials where sleep was a secondary outcome found no benefit at all. For CBD, results are mixed and product-dependent: a dedicated 150mg CBD-alone trial found no significant difference from placebo on core insomnia measures, while a larger 125-person trial of a CBD-terpene formulation found a small but statistically significant increase in deep and REM sleep. Adding THC to CBD produced opposite results in different populations across trials.
Does blue light before bed actually affect sleep?
The underlying mechanism is real — blue-enriched light can suppress melatonin and shift circadian timing under tightly controlled lab conditions. But evidence that blue-light-blocking glasses meaningfully improve real-world sleep is weak: a 2023 Cochrane review of 17 randomized trials found the evidence too inconsistent and low-certainty to draw a conclusion, and a 2025 meta-analysis of 3 crossover trials found no statistically significant change in sleep onset, total sleep time, efficiency, or nighttime waking. One 20-person trial even found objectively measured sleep time trended shorter with the glasses, despite better self-reported sleep.
What does sleep deprivation do to hormones?
A series of small controlled trials, mostly in healthy young men, found sleep restriction disrupts multiple hormone systems within days. Six nights at 4 hours of sleep raised evening cortisol and lowered thyroid-stimulating hormone in 11 men; just 2 nights of restricted sleep in 12 men lowered leptin (the fullness hormone) by 18% and raised ghrelin (the hunger hormone) by 28%; and a week of 5-hour nights lowered daytime testosterone by 10-15% in 10 young men. When researchers experimentally held cortisol and testosterone steady during sleep restriction in a separate trial of 34 men, resulting insulin resistance was cut roughly in half — suggesting these hormone shifts are part of the mechanism connecting sleep loss to metabolic harm, not just a side effect.
Does poor sleep affect metabolic health, and how quickly?
Faster than many people assume. In postmenopausal women, cutting sleep to 60% of normal for just 4 nights reduced insulin sensitivity by 12-20% in a randomized crossover trial using the gold-standard clamp method. In young men, 4 nights of 4-hour sleep induced significant hyperinsulinemia, hyperglycemia, and insulin resistance. Over a longer, more realistic 6-week trial, women whose sleep was cut by an average of 1.3 hours per night showed higher fasting insulin and worse insulin-resistance scores, with a stronger effect after menopause. Even isolated fat cells from sleep-restricted volunteers needed nearly three times more insulin to trigger a normal response after just 4 short nights.
New to this?
Start here for plain-English explanations of clinical trials, evidence levels, and how to read a study.