Taking Prilosec after bowel resection. Have depression and anxiety. Due to medication?

A 40 year old man underwent a bowel resection for a large diverticulem and some smaller ones. Approximately one year later he was hospitalized with severe abdominal pain and nausea . He was placed on Prilosec and life has been downhill ever since he began this medication. Shortly after beginning this med, he struggled with severe depression from which he has recovered to a degree but still struggles with depression and anxiety. This man never had any depressions issues prior to being placed on Prilosec or omeprazole and we are at wits end trying to help him. Can this RX be causing this depression problem and where do we start with doctors to enlist their help to help return him to the man he was prior to starting omeprazole.