Would almost 30 years in the military cause a personality disorder to develop?

He's been an officer for almost 30 years and due to annual deployments shows signs of PTSD. Based on the type of person he was before he joined the military, many of his old friends say he acts odd, like a person they've never met. He has a habit of lying, contradicting himself, looking down on others, showing no emotion and displaying other signs of narcissistic personality disorder. In other words, he's depressed and a possible narcissist. He's also been divorced for many years. Could his long military career have caused his dramatic change in personality?|||Yes. He probably hates himself for something he had to do, even if it was justified (or possibly not). He should seek help in some form of talk therapy, but it won't help until he wants to change, and he may not. Sometimes if life makes you an @$$hole people decide to stay an @$$hole for the rest of their lives.|||I have heard normally such problems occur to military men due to environment and circumstances which can easily treated by psychotherapy.|||Yes, but he was attracted to the military in the first place for a good reason probably. He is that person.