Casual sex doesn’t really work on a whole mind/body level. Neurochemical changes occur in both brains during sexual activity. These changes encourage emotional/limbic bonding. One reason females are more often hurt when a casual affair ends is that the female limbic system is larger than the males and she is more likely to become limbically connected. (Amen, Daniel G., MD. Change Your Brain Change Your Life. p 39-42. NY: Times Books, 1998.)