Ethel Emelia Hieronymus O’Brien was the daughter of Herman Engelbert and Minnie Julia Zellich Hieronymus. In 1939, she married George Thomas O’Brien (1895-1946) in New York. She was a 1933 University of Louisville School of Medicine graduate, and completed her residency at the Yale Institute of Human Relations. She began teaching in the UofL Department of Psychiatry in 1947. She retired as Assistant Clinical Professor Emeritus in 1989. Dr. O’Brien was appointed to the Jefferson County Juvenile Court in 1947. She was the first child psychiatrist employed by Kentucky mental hospitals in the 1950s.