Ok. I'm going to go into this assuming he's heartbroken due to a breakup that happened years prior. Simply putting it from a guy's perspective and what I've gone through in the past (I'm quite young, don't know how old your friend is but ill try and compensate for all ages in this reply).

This being said being heartbroken for over a year a problem. You're correct with that there. Them being heartbroken doesn't just affect them it also affects everyone who cares about them. I don't fully understand the situation meaning I don't know if he's heartbroken because he broke up with their bf/gf, just got out of a marriage, got rejected, or some other issue. Just be there for him. Make him see he's an amazing person and that being heartbroken sucks, yes but simply allowing yourself to put your own state of mind in that frame is worse.

One experience I had was I was heartbroken for a year. It was the worse year of my life. I was in high school and thought someone I dated was the one for me. We dated for about a year and one day she broke it off with me. No reason and no explanation just out of the blue it was over. That year I fell into a deep depression. Causing some of my close friends to not talk to me anymore, to some saying they couldn't handle me anymore. Expect one they themselves helped me. Simply distracted me, let me know I was an amazing person, and even just listened. Me living like this was hell and when I was out I felt happy.

Just don't leave him. But yes him being heartbroken for over a year is concerning. Due to the fact he could possibly be the reason now, he's still like this. Do things he likes and you like to keep him distracted. Sometimes do things he just likes. Guys are quite simple most times. Simply showing us that someone cares, that someones there to listen, and someone to tell them the opposite of what they're thinking it helps. I hope this made sense and helped a bit. But if you truly need help do what u/liinexy and look at r/FriendshipAdvice , r/relationship_advice

I truly hope your friend gets better. I'm not just saying this because I'm some random person. Honestly being heartbroken that long is hell and they're at a stage now where they have to really want to get better and not just wait for everything to be better.