The key word to this is trigger. When I first deployed to Iraq, my base was hit with mortars about 3 a day for 4 months. It became normal and eventhough a few tents down some fellow members were killed. I powered on and continued as it was nothing cause we had a mission to do. The scariest nights were when we didn't get hit and only heard the planes engine all night. But when I got back to my home station my first few weeks if you slammed a door I was hitting the floor. I was in the mall and someone dropped something and I dropped down. Friend of mine was like you need to go talk to someone but I couldn't cause you know that stigma of losing a top secret clearance over mental illness.
After 4 deployments being in locations I shouldn't of been cause my people didn't know what they were doing. I still powered through, trained as much as i could and continued business. And 9 years later after my last deployment, 5 years after I retired, I was talking with a friend. She asked me a question about one of my deployments and after I finished answering I just broke down. A situation I never told anyone about and I had to just get off the phone with her. I pictured every suicide and death that went down near me, reports of soldiers crossing the border(we were a mile from the border), helicopter flights over deserts with possible portable air missiles to shoot us down. Escorted to my base behind a truck with 6 dudes with their AK-47 pointed at us. Do you know how it is to wake up in the morning to go shower and use the bathroom on your 3rd day at a location. But the building is off limits cause a 19 year old kid took his 9mm and killed himself. Then the next day an Army soldier kills himself next door to us.
You cant tell someone when or why they should be depressed. Most people don't even understand why they are depressed just a trigger that kicks in and they can't control it.
Just like women with post partum depression. You cant tell her after the 3rd baby that she should be use to this be strong. She may of been depressed during the first two and fought through it. But now its hitting her, and hitting her badly.