I am very lucky that my bariatric study includes monthly visits with their psychologist, who is one of the most published researchers in the country on weight loss and bariatric related mental health issues. Here's the skinny. Your gut produces seratonin, and it produces it from carbs. Carbs literally can make you feel better mentally. In the immediate post surgery period, you're consuming virtually no carbs, and your gut has been altered. People with a tendency toward anxiety and depressive mood disorder could very well have some issues. Just like everything else, your body need time to adjust to your new gut chemistry. Nobody knows exactly how or where in the digestive tract psych meds enter the bloodstream, so for a fair number of bariatric patients, some trial and error with SSRI type medications is completely normal. At 1 year after surgery, about 40% of successful bariatric patients are on some type of psych med. it's just another possible complication that a good doctor/ medical team should prepare you for.