The research on intranasal oxytocin is genuinely mixed. Small lab studies found effects on trust, couples’ communication and fear responses, but the largest clinical trial found no benefit, several famous findings didn’t replicate reliably, and many studies were too small. This tracker summarizes 15 key studies so you can judge for yourself.
Not supported Autism · 2021
Daily oxytocin for 24 weeks in children with autism
Sikich et al., New England Journal of Medicine (2021) · Randomized, placebo-controlled trial, 24 weeks · 290 children and adolescents (ages 3–17)
Daily intranasal oxytocin did not significantly improve social or cognitive functioning compared with placebo. The largest trial of its kind, and a key reason to be skeptical of early small studies.
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Critique / methods Methods · 2016
Are intranasal oxytocin studies big enough?
Walum, Waldman & Young, Biological Psychiatry (2016) · Statistical review · Published intranasal oxytocin studies
Found that many intranasal oxytocin studies were too small to reliably detect real effects, meaning published positive results are likely to overstate the true effect.
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Critique / methods Methods · 2016
How much intranasal oxytocin reaches the brain?
Leng & Ludwig, Biological Psychiatry (2016) · Critical review · Review of pharmacology evidence
Argued that only a tiny fraction of a nasal dose is likely to reach the brain, and that some behavioral effects may come from oxytocin acting elsewhere in the body.
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Critique / methods Trust · 2015
Does oxytocin increase trust in humans? A critical review
Nave, Camerer & McCullough, Perspectives on Psychological Science (2015) · Critical review · Trust studies from 2005 onward
Concluded that the evidence that a single nasal dose reliably increases trust is weak, noting failed replications of the famous 2005 finding.
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Promising, early Appetite · 2015
Single dose and calorie intake in men
Lawson et al., Obesity (2015) · Randomized, placebo-controlled crossover · 25 men
A single dose modestly reduced how many calories men ate at a later meal, especially from fat. Small, short-term, and not a weight-loss treatment.
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Mixed or small Relationships · 2014
Oxytocin and couples' sexual experience
Behnia et al., Hormones and Behavior (2014) · Placebo-controlled, within-couple · 29 heterosexual couples
Effects were small: some participants reported modest changes in how intense or content they felt after intimacy, while most measures did not change.
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Promising, early Relationships · 2012
Partnered men and social distance
Scheele et al., Journal of Neuroscience (2012) · Placebo-controlled · Healthy men
Men in monogamous relationships who received oxytocin kept a greater distance from an attractive woman they had just met; single men did not. An interesting lab finding, not a clinical outcome.
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Promising, early Safety · 2011
Safety and side effects of intranasal oxytocin in research
MacDonald et al., Psychoneuroendocrinology (2011) · Systematic review of randomized trials · Dozens of randomized trials
Short-term doses used in research (roughly 18–40 IU) produced no reliable side effects or noticeable subjective changes in controlled settings. Long-term safety is much less studied.
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Mixed or small Autism · 2010
Emotion recognition in youth with autism
Guastella et al., Biological Psychiatry (2010) · Randomized, placebo-controlled crossover · Small sample of adolescent males
A single dose improved performance on a test of reading emotions from the eyes. Later, larger trials of repeated dosing were less encouraging.
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Promising, early Anxiety · 2010
Amygdala response in social anxiety disorder
Labuschagne et al., Neuropsychopharmacology (2010) · Placebo-controlled brain imaging · Adults with generalized social anxiety disorder and controls
Oxytocin dampened the heightened amygdala response to fearful faces seen in social anxiety. A brain-activity finding, not proof of symptom relief.
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Mixed or small Trust · 2010
Oxytocin and in-group versus out-group behavior
De Dreu et al., Science (2010) · Placebo-controlled experiments · Healthy men
Oxytocin increased trust and cooperation toward one's own group, and defensiveness toward competing groups. Evidence that oxytocin is not simply a 'be nice to everyone' hormone.
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Promising, early Relationships · 2009
Oxytocin during couple conflict
Ditzen et al., Biological Psychiatry (2009) · Double-blind, placebo-controlled · 47 heterosexual couples
Couples given oxytocin before a conflict discussion showed more positive relative to negative communication and lower cortisol (a stress hormone). Encouraging, but a single lab study.
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Mixed or small Anxiety · 2009
Oxytocin with exposure therapy for social anxiety
Guastella et al., Biological Psychiatry (2009) · Randomized, placebo-controlled trial · Men with social anxiety disorder
Oxytocin improved how participants rated their own speech performance, but did not improve overall therapy outcomes compared with placebo.
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Mixed or small Trust · 2009
Oxytocin, envy and gloating
Shamay-Tsoory et al., Biological Psychiatry (2009) · Placebo-controlled · Healthy adults
In a game of chance, oxytocin increased feelings of envy and gloating. Oxytocin seems to make social cues feel more important, in both directions.
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Mixed or small Trust · 2005
Oxytocin and trust in an investment game
Kosfeld et al., Nature (2005) · Double-blind, placebo-controlled · Healthy men
Investors given oxytocin entrusted more money to a stranger; the effect did not appear when they played against a computer. Hugely influential, but later replication attempts were mixed.
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