Depends on the friend, I think. Most of my closer friends have either experienced depression directly, or through another friend/relative - so, that element of shared experience surely helps in understanding & maintaining the relationship.

Having said that, I don't think it's a necessity to have depression as a shared experience - it depends on the depth of the friendship - a really good friend may not fully understand why I might be withdrawn, but would still see me as a friend, maybe based from the times when I wasn't feeling so depressed.

I can be very bad about maintaining friendships for the same sorts of reasons you listed, but the test for me has been those friendships that have been able to just restart where they were left off, maybe years later. They do exist, but they're uncommon treasures.

It is, however, hard for me to form new friendships & very, very hard when the depression is biting. Unfortunately, it's also very hard for me to lean on friends when it's biting. They may understand, but my inclination at those times is to hide.