Depression and Relationships (Romantic, Friends, Family, etc)

[Sen's Revenge]

At what point do you "give up" on someone who is clearly battling with depression, so much so that it takes a toll on your own life?

Non-hypothetical Example: I put together a care package for a friend who is having a rough go at it. (Nevermind what was in it, but you can believe it was thoughtful, fun, and while not terribly expensive, still more than I would spend on someone I liked less lol)

Well the package was sent back (no specific notice, was just marked Returned to Sender by post office), and he is not answering texts, phone calls, emails, or facebook messages. (I am not stalking him, but I did want to make sure he was not dead.)

Asked a mutual friend had he heard from him and he was like yeah, he posted in our GroupMe yesterday.

I know that his pattern is to retreat and not "bother" anyone else with his problems when he is experiencing stress and/or depression, and I can respect that, but I do feel as though I am owed an explanation about why this package was returned to me when I had just confirmed his mailing address not more than three weeks ago.

What do you all think?