Oxytocin
Sold as the cuddle hormone. It does rise around touch and sex. That it's what bonds you to someone hasn't been shown.
Oxytocin is a hormone, a chemical messenger in the body, and the one the internet calls the cuddle hormone. Levels go up around touch and around orgasm. Evidence: decent That's a correlation: it rises alongside closeness, which doesn't show it causes closeness. It's also hard to measure reliably in blood or saliva, so even the rise is a rough reading. Evidence: decent
The popular version goes further: a hug releases it, it makes you trust people, a spray of it up the nose will make someone bond with you. Tested with nasal sprays, it doesn't reliably raise trust or bonding. Evidence: decent
The same articles usually add that early love looks like cocaine in the brain and like OCD, obsessive-compulsive disorder, in the blood. The cocaine line is a comparison with a separate study, not a test. People in love were scanned, cocaine users weren't; the real finding is under dopamine. Evidence: decent The OCD line is one small 1999 study that measured a protein that handles serotonin, another chemical messenger, on blood cells rather than in the brain, and it hasn't been repeated at scale. Evidence: worth trying
Why it matters
What holds up is the touch, not the hormone. In one small study, married women waiting for a possible electric shock showed less threat activity in the brain while holding their spouse's hand, and more so the better the marriage. Only women, and nobody measured oxytocin. Evidence: decent Touch calms the body. Evidence: decent Oxytocin may be part of why, but that's the weak link in the story. Evidence: worth trying Skip the chemistry and try a long hug.