I remember watching a sociology course a few years ago, and one of the lectures discussed the study of suicide by a man called Emile Durkheim. It covered a lot of ground, but essentially what it boiled down to was that the more isolated you are, the more likely you are to commit suicide. Single people are more likely that people in a relationship, people without kids vs those with kids and so on. The lecture also discussed another finding Durkheim came across: Men commit suicide more often than women.
One of the interesting things the lecturer pointed out was that men's social networks often depend upon their partners. This of course isn't true in every case, but often men's social engagements are organised by their partners and their friends are generally the partners of their partner's friends. Thus, a break up or divorce is incredibly traumatic as their one connection to the outside world has been severed and they're now isolated. You combine this with the fact that men in the west are often raised in a way that "bottles up" their emotions and you have men that even when they do have some type of support network, they can't leverage it due to social norms making pushing against them seeking emotional support.
As I mentioned in a previous post, as I've gotten older I've not kept up with making new friends to replace the ones I've lost. I am now in a position where I literally have no friends. I have a few "acquaintances" that I would call friends in casual conversation, but no one who if shit hit the fan I could call up and expect help when I asked for it. My only form of socialisation is through my partner, and while I don't expect us to break up - I am very aware that I am connected to the rest of the world by a single thread.
Because of this, I have been trying to increase my social activity. I've recently gotten involved in a meet up, and I think I will start attending others as I find them. This isn't enough though, I need to make some meaningful relationships - this is a lot harder. I do hope I make some more friends because I know I need it. I've been seriously depressed before, but not in a very long time. The reason for this is that I now have a meaningful relationship with another person: my partner. This is also why I am aware that if anything every happened to us, I know exactly what is in store for me and I don't want to be in a situation where I am left alone, with no one to really turn to.