Should I stop trying to help and contact a good friend?

I apologize for the length in advance, but I’d greatly appreciate any advice on this matter- it’s really hurting me.

I am in a triumvirate of best friendship. The other two of us live in my hometown which is about 2.5 hours away. They live next to each other in a double house. I don’t see them nearly as much as I’d like to. I don’t know how to express to you how close we all are, but I can honestly say that both of them are on my list of 5 people I’d give my life for. We always said whichever of us would die first, the other two would make a cake out of our ashes and eat it… we’re also kind of gross.

Now, the friend in question, Matt, is in “retreat” mode which he slips into once in a while. He will not answer phone calls or emails and will not talk to anyone until he’s ready, including me and our other best friend, even though he lives right next door. The last time I talked to him was in July when we all went to the beach together. The only interaction we’ve had since is a text message that he sent. It said “I miss you.” I called him immediately after I got it and he didn’t pick up.

I know that his depression is a big part of this and it gets worse when he’s in financial trouble. He has an excellent job, but most of his wages are garnished for his massive- I mean massive debt. There are other reasons for his depression, but mostly it’s money, I think.

The friend who lives next door to Matt just says, “Well, you know how he is…” He says he hears him coming and going so he knows he’s alive when he hasn’t talked to us in a while.

My question, I guess, is should I continue to try to contact him, and what, if anything, should I do to help him? Maybe he needs the space, but maybe space is hurting him more. I love him so much, and I know he doesn’t intend to hurt me, but it’s becoming painful to be his friend. It’s painful to watch him hurting, it’s painful to keep being rejected by him, and it’s painful to miss him all the time.

Just to be clear, it’s not just me that he’s not in contact with, though I fear I get it even worse since I live so far away. He doesn’t talk to any of our friends. Family is out of the question in terms of help. He has none, to speak of.