SAS: Who Dares Wins star Jason Fox has told how soldier friends have suffered PTSD after serving in Northern Ireland.
Jason - who himself battled back from being suicidal after missions in Afghanistan - now works with a charity for veterans called Rock2Recovery.
The former Special Forces operative said that earlier in his career he met men so scarred by bombs and violence that "the most innocent of happenings would emotionally transport them back to 1980s Belfast".
Jason (41) said: "Some of the blokes I knew in the early phases of my career were old enough to have served in Northern Ireland. They'd been subjected to mob attacks, petrol bombs and group protests that had turned incredibly violent without warning.
"Having retired, some of them were affected negatively by a normal occurrence at a civilian event: a raised voice in a party, a crying baby in a pram or the sound of two shopping trolleys colliding in a supermarket were among the catalysts for responses ranging from deep depression to violence.
"The most innocent of happenings would emotionally transport them straight back to 1980s Belfast, working amid The Troubles.
"I've also met people who have been deeply affected by an outbreak of violence in a peacetime setting."
In his new book, Life Under Fire, the ex-Royal Marine explains that soldiers are "taught to watch out for 'combat indicators': signs that trouble is nearby or that an enemy attack is imminent".
He explained: "Having spent a few years helping battle-broken men and women with Rock2Recovery, not to mention some of the recruits on SAS: Who Dares Wins whose lives had taken shocking and unimaginable twists, I've come to know the combat indicators for mental health. It's sometimes easier to spot them in another person because the brain can become so stressed out and fatigued that it doesn't always recognise an ambush closer to home.
"My own experience of mental health issues followed a common pattern: I became withdrawn, angry and fuzzy-headed.
"I could be very forgetful, too, to the point that, having told a friend one night that I was driving around looking for a tree to hang myself from, the following day, when that same friend called to check on my state of mind (luckily I'd been coaxed home), I couldn't remember my behaviour or the frantic conversation we'd had.
"Despite those emotional warning signs, it would be a while before I sought help. For months I shrugged off people's concerns; I ignored the danger I was in because I couldn't really see it myself, and I was only fixed once a work colleague had actively nudged me in the direction of a good therapist.
"Cleared of the stress from my misfiring head, I became aware of a series of signals that would have encouraged me to seek help at a much earlier stage, had I understood them.
"Following an extreme event - a physical assault or a car crash, for example - our brains can go into self-protection functionality: we look for danger when there is none, such as in a crowded supermarket or pub."
If you are affected by these issues, contact the Samaritans on 116 123, or Lifeline on 0808 808 8000.