"Views concerning the main causes of suicide have differed widely, but hardly anyone denies that re-directed aggression is a major factor. ..
There is a lower rate of suicide during times of war. The suicide curves for the present century show two huge dips during the periods of the two world wars. In other words, why kill yourself if you can kill someone else? It is the inhibitions about killing the people who are dominating and frustrating the potential suicide that force him to re-direct his violence. He has the choice of killing a less daunting scapegoat, or himself. In peace-time, inhibitions about killing make him turn most often towards himself, but during war-time he is ordered to kill, and the suicide rate goes down.
The relationship between suicide and murder is a close one. To a certain extent they are two sides of the same coin. Countries with a high murder rate tend to have a low suicide rate, and vice versa. It is as if there is just so much intense aggression to be let loose, and if it does not take the one form it will take the other. Which way it goes will depend on how inhibited a particular community is about committing murder. If the inhibitions are weak, then the suicide rate goes down. It is similar to the war-time situation, where inhibitions against killing were actively and purposely reduced."
Page 40, 41. "The Human Zoo", by Desmond Morris