In many contexts “How are you?” Is just a social nicety and its used just like saying hello. In those cases, don’t overthink it wishing they want a detailed answer if they dont. If they do seem to want to know, but wont understand anything too intense “I could be better” seems to fill the bill. Then they can ask another question if they want to draw you into conversation. This used to irritate me, but there are many things that are really disturbing in life, so why sweat the small stuff. Very early on , my mother taught me to smile in a casual context no matter if I was depressed (she understood depression having had it) and I think she was right. You get a better response from people, and in fact I think there are some studies that show that flexing the smile muscles in your face actually give you some endorphin hormones and make you feel better.