Oxytocin

What oxytocin is

Oxytocin consists of 9 amino acids, is formed in the hypothalamus and released into the blood via the pituitary gland. The name literally means quick birth. In medicine it has been used for decades to trigger labor and promote milk flow; as an infusion it is a standard medicine in obstetrics.

In addition, oxytocin acts as a messenger in the brain. It is involved in the bond between mother and child, in pair bonding and in trust. It is released during birth and breastfeeding, but also during touch and closeness. That is where the nicknames cuddle hormone and trust hormone come from.

From cuddle hormone to longevity candidate

The work that put oxytocin on the longevity map comes from the laboratory of Irina and Michael Conboy in Berkeley. In 2014, Elabd and colleagues showed that oxytocin is needed for the regeneration of skeletal muscle and that its level in the blood falls with age. When oxytocin signaling was blocked in young mice, the muscles regenerated less well. When old mice received oxytocin, regeneration improved rapidly, because the muscle stem cells were activated via the MAPK/ERK signaling pathway. Mice without oxytocin developed premature age-related muscle wasting.

Further findings fit into this picture. In a small study, women with severe postmenopausal osteoporosis had lower oxytocin levels than healthy women, and the levels were related to bone density. Researchers at MIT found in mice that the gut bacterium Lactobacillus reuteri increases oxytocin release via the vagus nerve and made wounds heal in half the time. Bonding and repair evidently run via the same messenger, an appealing idea that so far is supported mainly in animals.

How the scene uses it

In US clinics and in the biohacking scene, oxytocin is used as a nasal spray or lozenge, for stress resilience, mood, as an accompaniment to couples therapy and increasingly with a view to muscles and bones in old age. In Germany oxytocin is prescription-only; nasal spray forms come via compounded preparations. Users report more calm, warmth and closeness; these are user reports.

The route without a spray is also popular. Touch, massage, sex, breastfeeding, singing together, time with the dog or warm baths are considered natural triggers. That social connectedness is good for health is well supported: a meta-analysis of 148 studies with 308,849 participants found a 50 percent higher likelihood of survival with strong social relationships. What share oxytocin has in this is open, but this route cannot do any harm.

What the studies show

Trust in the investment game, Nature 2005

Kosfeld and colleagues gave subjects oxytocin or placebo as a nasal spray and had them play a trust game with money. Under oxytocin, participants entrusted considerably more to others. The effect was not based on a generally higher willingness to take risks, but concerned the social risk in dealing with other people. A critical review from 2015, however, concluded that precisely this finding could not be replicated well. A large, pre-registered preprint from 2025 again found around 15 percent more trust in 359 people with low baseline trust.

Muscle regeneration in mice, Nature Communications 2014

Elabd and colleagues showed that oxytocin is an age-dependent hormone in the blood that is needed for the maintenance and regeneration of muscle. Blocking it in young animals worsened regeneration; administering it to old animals improved it via activation of the muscle stem cells. Without oxytocin, premature muscle wasting occurred. The authors point out that oxytocin is already an approved medicine.

Autism: SOARS-B, New England Journal of Medicine 2021

Sikich and colleagues randomized 290 children and adolescents aged 3 to 17 with autism spectrum disorder to oxytocin nasal spray or placebo for 24 weeks. The score for social withdrawal fell almost equally in both groups, by 3.7 and 3.5 points; the difference was not significant. The secondary outcomes did not differ either, and side effects were similarly frequent in both groups. A smaller study in 87 children aged 3 to 12 likewise found no effect overall, only an indication of benefit in the 3- to 5-year-olds.

Where the data stop

The hype around the trust spray was greater than the evidence. The early, small studies on trust and social behavior could only partly be replicated, and the largest study in autism was negative. In addition, there is a measurement problem: determining oxytocin in the blood is methodologically difficult, the values fluctuate strongly, and the 2015 review considers the plasma data to be error-prone. Anyone who has their own level tested therefore learns little.

The bodily effects on muscle, bone and wound healing rest on a solid basis of animal and mechanistic data. Controlled studies on whether oxytocin slows muscle loss or bone loss in older people do not exist so far. The osteoporosis data are observations in 20 patients and 16 healthy women and show an association, not a cause. The reuteri findings also come from mice.

Status, approval and legal

In Germany, oxytocin is approved as a prescription-only medicine for obstetrics. Use as a nasal spray for mood, bonding or longevity is off-label; dosage information is therefore omitted. Nasal sprays are produced as compounded preparations. Gray-market products raise particular questions about purity and content for a sensitive peptide. Oxytocin is not listed on the Prohibited List of the World Anti-Doping Agency.

Safety

Used briefly and at low doses, oxytocin nasal spray is considered well tolerated. In the large autism study, side effects did not occur more frequently under oxytocin than under placebo. Occasional nasal irritation and head pressure are reported, rarely a drop in blood pressure or fluid retention, because oxytocin is related to the hormone that controls water balance. Outside obstetrics, oxytocin is off-limits in pregnancy because it can trigger labor. Anyone with cardiovascular disease or taking medication that affects water and salt balance should discuss use with a doctor. Long-term data on regular use as a nasal spray in healthy people are missing.

Sources

• Kosfeld M et al., Nature 2005 — oxytocin and trust
• Nave G, Camerer C, McCullough M, Perspectives on Psychological Science 2015 — critical review of oxytocin and trust
• Vogt B et al., preprint PsyArXiv 2025 — oxytocin and trust in 359 people with low baseline trust
• Elabd C et al., Nature Communications 2014 — oxytocin and muscle regeneration
• Scheele D et al., Journal of Neuroscience 2012 — oxytocin and social distance in men
• Poutahidis T et al., PLoS One 2013 — Lactobacillus reuteri, oxytocin and wound healing in mice
• Sikich L et al., New England Journal of Medicine 2021 — SOARS-B, 290 children and adolescents with autism
• Guastella AJ et al., Molecular Psychiatry 2023 — 87 children with autism
• Breuil V et al., Joint Bone Spine 2011 — oxytocin and postmenopausal osteoporosis
• Holt-Lunstad J et al., PLoS Medicine 2010 — social relationships and mortality, meta-analysis