I don't understand much about mental health issues but I am aware of anxiety and depression. I've never considered myself depressed but I get a little down now and again but I just see that as normal.
However, I go through phases of obsessing about silly things. This can often stem around friends of colleagues. For example, recently my best friend hadn't messaged me for 3 days (we usually text daily) so I worried about this for days and had convinced myself she had fallen out with me or that I had done something wrong. It really stressed me out and almost ruined my weekend. Another friend a few months ago had cancelled catching up and I convinced myself she was mad at me.