For a long time it was believed that stress was the main culprit for chronic ulcers. My mother was told that. It made sense since she was very unhappy for years about her permanent move to the U.S. away from her family, culture, language, everything.

Well, there was a lone medical researcher in Australia who believed that spiral gastric bacteria could be the cause, as it was found in the majority of peptic ulcer patients.

"1984 was a difficult year. I was unsuccessfully attempting to infect an animal model. There was interest and support from a few but most of my work was rejected for publication and even accepted papers were significantly delayed. I was met with constant criticism that my conclusions were premature and not well supported. When the work was presented, my results were disputed and disbelieved, not on the basis of science but because they simply could not be true. It was often said that no one was able to replicate my results. This was untrue but became part of the folklore of the period. I was told that the bacteria were either contaminants or harmless commensals.At the same time I was successfully experimentally treating patients who had suffered with life threatening ulcer disease for years. Some of my patients had postponed surgery which became unnecessary after a simple 2 week course of antibiotics and bismuth. I had developed my hypothesis that these bacteria were the cause of peptic ulcers and a significant risk for stomach cancer. If I was right, then treatment for ulcer disease would be revolutionized. It would be simple, cheap and it would be a cure. It seemed to me that for the sake of patients this research had to be fast tracked. The sense of urgency and frustration with the medical community was partly due to my disposition and age. However, the primary reason was a practical one. I was driven to get this theory proven quickly to provide curative treatment for the millions of people suffering with ulcers around the world.
Becoming increasingly frustrated with the negative response to my work I realized I had to have an animal model and decided to use myself. Much has been written about the episode and I certainly had no idea it would become as important as it has. I didn’t actually expect to become as ill as I did. I didn’t discuss it with the ethics committee at the hospital. More significantly, I didn’t discuss it in detail with Adrienne. She was already convinced about the risk of these bacteria and I knew I would never get her approval. This was one of those occasions when it would be easier to get forgiveness than permission. I was taken by surprise by the severity of the infection. When I came home with my biopsy results showing colonization and classic histological damage to my stomach, Adrienne suggested it was time to treat myself. I had a successful infection, I had proved my point."

He also healed himself through anti-biotics.

Barry J. Marshall...one of the heroes of medicine.

https://www.nobelprize.org/prizes/me.../biographical/

P.S. This was in the mid-1980s. Eventually my mother was tested, had the bacterium, got the right antibiotics, and the peptic ulcers disappeared.