How to communicate with depressed friend

Dear Carolyn: When a friend is not contacting you due to a depression, what are the best ways to “deal” with it, so to speak, in order to keep the friendship strong throughout the absence? For example, an occasional inquiry into well-being or message of support may be heartening, while too many may cause unnecessary emotional burden and guilt for the depressed one.

I would be interested to hear from others who have experience on either end of this sort of relationship, and how they managed to maintain or regain ties to others during or after a depression. This friend of mine is long-distance, so I do not have every strategy at my disposal.

— Long-Distance Friend