"New Scientist magazine reports that Stuart Brody, a psychologist at the University of Paisley, found having sex can help keep stress at bay. However, only penetrative intercourse did the trick — other forms of sex had no impact on stress levels at all.

... Volunteers who had had penetrative intercourse were found to be the least stressed, and their blood pressure returned to normal faster than those who had engaged in other forms of sexual activity such as masturbation. "