I have written elsewhere on here that people leaving are suddenly left to fend for themselves (accomodation, often food etc) in a way that they previously did not have to. At the same time they lose touch with all their friends. Finally there is the fact that they may have had 'issues' before they joinbed up which were never solved, just suppressed by the forces life.
Often the armed forces organisations would actually be able to offer help. unfortunately at first the servicemnan is proud and believes he can cope. He then sinks slowy into trouble and is reluctant to seek help because his pride will not let him admit to forces how low he has sunk
In the shelters I tried to help a few but they would not let me contact anyone connected with forces. Their psychological issues are not sufficient to make them a danger to anyone else so they are left for 'care in the community'.
I remember particularly one infantry ex-NCO, good boxer. He had a flat but came to the shelter for food and most importantly company. Watched him die, week by week