PTSD or being 'Shell-Shocked' has been known about and recognised for 100 years since the first world war.
There are historical references to the symptoms of PTSD going back much further. It was, at one time, known as 'Soldier's Heart'. Shell Shock was the WW1 name, then came 'Lack of Moral Fibre (LMF)', now shown to have been invented as a way of using shame and guilt to keep bomber crews flying.
Suicide is indeed the biggest cause of death amongst 25-45 males in UK, and the second biggest in the 16-24 range (the biggest for them is RTCs). Interestingly, suicide rates amongst males over 64 is showing an upward trend.
I won't criticise Santaman2000 for his views, though I think they are wholly incorrect. Although it's getting better, there is still a great deal of stigma and discrimination around poor mental health. You can see someone with a broken leg, for example, and so it's easy to understand, whilst someone experiencing poor mental health may have no visible signs. There is still a great deal that's not well understood. There are so many factors that affect mental health, from neurobiology to genetics, social factors and life events.
In terms of PTSD, it's generally seen as something that affects military personnel, but in fact the prevalence is about the same amongst civilians. It's the individual's perception of an incident that makes the difference. It can affect anyone - so there but for the Grace of God, etc. And there are people who pretend to have it; it's almost become the acceptable face of poor mental health. I'm certainly aware of people who have tried to garner sympathy from others by saying they have PTSD, and some who use it to try to excuse bad behaviour. These people can rarely convince professionals, however, and it's usually quite simple to catch them out.
The idea that there is some sort of enormous conspiracy involving all the world's mental health professionals and researchers is, however, risible. An unshakeable belief in something that is patently untrue is a delusion, and delusions are a symptom of psychotic illnesses - unless, of course, they don't exist either . . .