Dr. Kirby was born in Goldsboro, North Carolina, the son of a physician who had been superintendent of the Goldsboro State Hospital. He graduated from the University of North Carolina (1896) and received his M.D. (1899) from Long Island College Hospital (N.Y.).
Dr. Kirby entered psychiatry at Worcester (MA) State Hospital under Dr. Meyer and went with Dr. Meyer to the New York Psychiatric Institute as an Associate in Clinical Psychiatry (1902–08), when he was appointed Director of Clinical Psychiatry at the Manhattan State Hospital. While in this position, he prepared a classification of the psychoses, which was used in the 1917 Statistical Guide and later adopted by the American Psychiatric Association. In 1917, he served briefly as Medical Inspector for the New York State Hospital Commission, following which he was appointed Director of the New York State Psychiatric Institute, where he remained until 1931. At the Institute, he expanded clinical studies and research activities and saw the Institute become affiliated with the Columbia Presbyterian Medical Center. He was a strong advocate of a psychodynamic approach in the treatment of mental disorders.
Dr. Kirby served as President of the American Psychiatric Association (1933–34).