Depression and gastric. Such situation?

My father is a High BP and type 2 diabetes patient. Recently he experienced rapid memory loss, concentration issues, anxiety along with gastric issues (which we thought is not a major problem). we consulted a doctor (1 month ago) who diagnosed that my father is suffering from depression. He prescribed following medicines: Censpram 10mg, Ezolac .25 mg, Nexstar and Rabemac DSR. They had positive effect on my father's condition. But last week doctor asked to stop taking Rabemac DSR as he want facing any gastric issues any more. It has been 5 days and my father haven't taken this medicine but his condition is back to the way it was 1 month ago. He has continuous mild headache, difficulty in recalling words, names etc. like he was having before. I wish to know that, are depression and gastric issues related? What precautions are to be taken in such situation? What medicine can be prescribed in such situation?