Probably. If he never had this before and he does now, you can at least speculate there is a connection. What does his doctor say?
Excess consciousness of saliva and of swallowing can also be a psychological response to something, kind of a cousin of OCD, even if it's a psychological response to actual trauma. But if he's actually having to cough a lot, clearly there is more saliva than there used to be, going through his pipes. So I wouldn't let his doc blow it off by saying it's all in his head.