Our 2 1/2 year old female domestic shorthair has phases that happen every couple of months where she isolates, seems lethargic, and loses interest in food for 2-3 days. The first time it happened we were just about to take her to the vet when she snapped out of it. In between these episodes she acts very normal. She does not have any other symptoms (i.e. no vomiting, diarrhea, congestion, etc. She does seem to lose weight during these phases but then gains it back afterward.
Does anyone have any thoughts on what could be going on??