A study in the current issue of Hormones and Behavior looked at the physical effects of social closeness on women. The results suggest that emotional closeness to a friend increases progesterone, a hormone thought to “boost well-being and reduce anxiety and stress.”
Stephanie Brown of the University of Michigan (the lead researcher of the study) paired up 160 female college students. She randomly assigned pairs of women to a task designed to elicit emotional closeness or to an emotionally neutral task (editing a botany manuscript). Progesterone levels were measured afterwards. The hormone levels of pairs who were involved in the emotional task remained stable or increased. A reduction in progesterone was found for pairs in the neutral group. Here’s the interesting part: A week later, the pairs met again and played a card game with their original partners. The researchers then asked the participants how likely they’d be to risk their life for their partner. Higher levels of progesterone were linked to a greater willingness to sacrifice to help their partner. It was noted that previous research had linked higher levels of progesterone to a desire for social bonding, but this was the first study to find that the reverse was also true.