I'm not going to dismiss this notion out of hand. I do very much believe that humour can be a potent coping mechanism. Even in the saddest circumstances I have been part of, among mourners there can still be that spark of humour that keeps them going and mutually supportive.
There is most certainly not going to be a blanket solution; for some it would work and for others it would not; what works for some would not be the same as what works for others. Great care would be needed to no misapply it, as the mental harm could be significant.
But I do very much believe that humour is an evolved trait for a reason, and not just by happenstance.