Your question is far from dumb. I had a close friend who withdrew from me due to depression. She never admitted it but as I knew she had suffered from depression prior to her cutting contact I figured that's what it was. When she got back to me, she denied it and just stated that's what she "does" sometimes, she tends to feel "suffocated" and It confuses her also. She likes to save face but at the time I believed her excuse and got angry with her because It was at a time I thought I needed her the most. That, I regret as a few few months later after dealing with depression for a while I became significantly worse had the same types of feelings she had explained to me. I had no desire to speak to or be with friends and I always socially withdrew without explanation. My friend and I don't speak anymore and we were very close and I miss her very much so I think It's safe to say that depression can cause a change in friendships/relationships