It is clear that to our primitive ancestors - who evolved the fight/flight response - it was a simple matter of survival that when the body began responding to danger, sexual activity should cease. It would not have aided survival, after all, for them to have been so intent on pleasuring each other that both became a meal for a passing predator.

The autonomic nervous system has two parts to it - one produces increasing alertness and prepares for action, the sympathetic nervous system. The other is about winding down, rest, recovery and healing - the parasympathetic nervous system. Both are active all the time, apparently working against each other. It is the balance between these which produces our various states of stress and relaxation.

In fact, both are involved in the act of making love. The parasympathetic nervous system mediates the process of sexual arousal. The process of ejaculation is a sympathetic nervous system process. So the fight/flight response will prevent arousal in the first place, or if a man is already aroused will cause him to lose his erection, or to ejaculate sooner than desired. So the two main sexual problems which men experience are explained. Similar processes produce the female problem of frigidity.

Many cases of sexual dysfunction are resolved once stress levels are once more at normal levels, although occasionally further work has been required.