To his Mexican immigrant family, Paul Lozano was a star. A brilliant and shy student from El Paso, he had gained entry to one of the nation's most elite institutions: Harvard Medical School. His future seemed assured. But during his third year of studies, Lozano became homesick and depressed. He got a list of Harvard-recommended therapists and called the first name on the alphabetical roster: psychiatrist Margaret Bean-Bayog. A clinical assistant professor at the medical school, she had a reputation as a gifted lecturer and dedicated researcher into substance abuse.
But what followed for Lozano, his grieving family claims, was a...