The rise of the biological causation model in the past thirty years is traced to psychiatry’s efforts to regain lost status and to protect itself from intrusions by non-medical practitioners, as well as to the pharmaceutical industry’s drive for profits. Evidence in support of the model, including studies of identical twins and of brain structure and function, are less revealing than was earlier thought, due to problems in methodology and interpretation. Organized psychiatry, when challenged in 2003, was unable to provide compelling evidence for biological causation of most mental and behavioral disorders. A paradigm shift away from biological causation and toward environmental causation is called for.