Sarah is 57 years old and has lost her husband to prostate cancer 6 months ago. She comes today for her review appointment since commencing Sertraline. Her mood remains low but is better compared to before and she continues to describe feeling anxious. Her appetite is slightly better, but she has now dropped a dress size despite eating more regularly. She denies any dysphagia but is complaining of indigestion which has little relief with Gaviscon.
She is an ex-smoker and drinks no alcohol. Abdominal examination is normal.
What is the most likely diagnosis?