Blabla: It’s a Machlokes Haposkim. We generally seem to assume that the Mitzvah is connected to the Mitzvah of fasting and that they go together (they are Darshaned from the same Possuk-sort of). In the vast majority of cases, it can’t hurt to eat so the person should eat a lot just in case. In your case, do whatever your doctor/psychiatrist/Rabbi (preferably after all three discuss with each other if possible) tells you to.
