Oxytocin is a nine-amino-acid peptide hormone made in the hypothalamus and released from the pituitary gland. Its established jobs are plain: it drives contractions of the uterus during labour and the let-down of milk during breastfeeding. It was the first peptide hormone to be made synthetically, by Vincent du Vigneaud in 1953, work that earned the 1955 Nobel Prize in Chemistry. Synthetic oxytocin is an approved drug in most countries, sold as Pitocin in the United States and Syntocinon elsewhere, to induce or strengthen labour and to control bleeding after delivery. The research covered here is about something else: the claim, which took off in the 2000s, that oxytocin shapes trust, bonding and social behaviour, and what happened when people tried to confirm it.

OxytocinWhat the studies show

Q: What kind of evidence exists for oxytocin?

Mixed evidence. A well-characterised hormone and approved obstetric drug; for social behaviour, a 2005 nasal-spray result that a registered replication and a 290-person autism trial failed to confirm.

The hormone of labour wards and the "trust molecule" headlines — and the registered replication that found no effect on trust at all.

5 min read · Mixed evidence · Updated November 2026

In short

Name: oxytocin
Evidence: Mixed evidence
Bottom line: A well-characterised hormone and approved obstetric drug; for social behaviour, a 2005 nasal-spray result that a registered replication and a 290-person autism trial failed to confirm.

Before you read this

This guide explains what published studies found. That is all it is.

It is not medical advice and it is not instructions for using anything. Where a dose appears, we are reporting what a named study gave the people or animals in it — a fact about the study, not an instruction to you.

The compounds here are not approved by the FDA for use in people and are sold for laboratory research only. A study tells you what happened to the subjects in it; it does not tell you what would happen to you. Talk to a doctor first.

What it is

Oxytocin is a nine-amino-acid peptide hormone made in the hypothalamus and released from the pituitary gland. Its established jobs are plain: it drives contractions of the uterus during labour and the let-down of milk during breastfeeding. It was the first peptide hormone to be made synthetically, by Vincent du Vigneaud in 1953, work that earned the 1955 Nobel Prize in Chemistry ¹. Synthetic oxytocin is an approved drug in most countries, sold as Pitocin in the United States and Syntocinon elsewhere, to induce or strengthen labour and to control bleeding after delivery. The research covered here is about something else: the claim, which took off in the 2000s, that oxytocin shapes trust, bonding and social behaviour, and what happened when people tried to confirm it.

The rest of this guide is free

Unlock the Oxytocin guide — and every other one

What the studies found, what they didn't, every source linked. Enter your email once; the link we send opens all of them on this device, plus one plain-language study breakdown a week.

Dogs and their owners

The most charming study is from Japan. In 2015 Nagasawa and colleagues reported in Science that when dogs and their owners spent 30 minutes together, the pairs in which the dog gazed at the owner the longest showed the biggest rise in oxytocin in the owner's urine, and in the dog's too. Hand-raised wolves did not gaze at their human carers in the same way and showed no such rise. In a second experiment, oxytocin sprayed into the noses of dogs increased gazing in female dogs, and their owners' oxytocin then rose in turn ². The authors proposed a loop between the two species, shaped by domestication, in which each partner's hormone feeds the other's behaviour. It is a study of a hormone that occurs naturally; it says nothing about what giving oxytocin to a person does.

The trust study and what happened next

In 2005 Kosfeld and colleagues published "Oxytocin increases trust in humans" in Nature. Male students received oxytocin or placebo as a nasal spray and then played an investment game with real money; those on oxytocin handed more to an anonymous partner, and 45% of them showed the maximum level of trust against 21% on placebo ³. The paper became one of the most cited in social neuroscience and set off hundreds of nasal-spray studies of empathy, generosity and bonding.

The replication record has not been kind. A 2015 review in Perspectives on Psychological Science went through every published attempt and concluded there was no robust evidence that oxytocin raises trust in people; it also raised the unresolved question of whether oxytocin sprayed into the nose reaches the brain in amounts that matter ⁴. In 2020 a registered replication in Nature Human Behaviour, with the original study's senior author among the co-authors and a sample several times larger, ran the same game and found no effect of oxytocin on trust ⁵. The pattern is familiar from other corners of psychology: small studies with flexible analysis produce positive results that disappear when the study is repeated at proper size with the analysis fixed in advance.

The autism trial

The largest clinical test of the social-behaviour idea was a 2021 trial in the New England Journal of Medicine. It randomised 290 children and adolescents with autism to daily intranasal oxytocin or placebo for 24 weeks, with social behaviour as the primary outcome. There was no difference between the groups ⁶. Earlier, smaller trials had reported effects in both directions, which is what a null result at scale usually looks like from the ground.

What this adds up to

Oxytocin the hormone is real, well understood, and an approved drug for a specific job in obstetrics. Oxytocin the "trust molecule" is a claim from small studies that did not survive a registered replication or a large placebo-controlled trial. Nasal oxytocin is not approved anywhere for any behavioural or psychiatric use, and the question of whether it even reaches the human brain in meaningful amounts remains open.

What these studies are, and aren't

Mixed evidence. A well-characterised hormone and approved obstetric drug; for social behaviour, a 2005 nasal-spray result that a registered replication and a 290-person autism trial failed to confirm.