I found the same thing in my life, the friends just slipped away as I know they were not interested in listening to my woes and I think my talking openly about my depression made them feel uncomfortable and I was no longer the life of the party.
As far as relatives out of town, it is like "out of sight, out of mind". They are not seeing it first hand so they just don't think about it much. I know I have made that mistake myself and I have learned the hard way.
I now pay attention and listen when someone is upset or depressed. I don't run from them, I stay and let them vent, cry or whatever will help them.
Take care my friend, we are here for you.