It has been noted that during war time there tends to be a significant drop in the suicide rate. This has been reported in many different countries so it seems to be a universal phenomena. One theory is that this decline is due to the social cohesion that war creates.
An alternative theory can relate to the idea of suicidal ambivalence. All suicidal individuals are ambivalent to some degree - “I do want to die vs I do not want to die”.
All suicidal people have this contradictory set of thoughts and urges inside themselves. The suicidal individual has percentages of both with the levels waxing and waning over time. Sometimes it will be 50/50 and then on other days it might be 60/40.
In war time or when there is an external threat to life the FC aspect of the personality could be stimulated as people tend to think more about how they are going to survive this period of threat. All those around them would be doing the same. This would make the FC part more prominent in the personality and hence the AC urges to die diminish and the suicide rate drops.
This could be further supported by other data as well. In Australia some of the highest rates of suicide were during times of depression and the lowest during the war years. In Serbia the highest rate of suicides recorded were during the hyper-inflation period and the lowest during the NATO bombing in 1999.
It could be argued that during times of economic hardship there is not so much a threat to life but a threat to the standard of living. People have to live with hardship but their lives generally are not under direct threat as can happen in war time. Hence in times of economic depression the FC is not stimulated as it is during war.