Spanking your partner may ratchet up their stress hormones, but they’ll thank you when it’s over, according to a new study. Researchers measured levels of the stress hormone cortisol in 13 men and women at one S&M party, and testosterone levels at another. Those on the receiving end saw cortisol rise, the New Scientist reports, and women saw testosterone increase. But levels dropped afterward, and couples reported increases in relationship closeness.
“When sexual intercourse is consensual it is not stressful—even if it is extreme sex,” concluded one researcher. But one psychologist notes that nearly all shared activity brings couples closer. “It doesn't have to be tying up your partner or placing clamps on their nipples,” he said. “It could be something as simple as cooking a meal together.”