Dr. John W. Barnhill is DeWitt Wallace Senior Scholar, Professor of Clinical Psychiatry, and Professor of Medical Ethics at Weill Cornell Medicine. He is also Adjunct Clinical Professor of Psychiatry at the Columbia University College of Physicians and Surgeons and an Attending Psychiatrist at New York Presbyterian Hospital.

Dr. Barnhill serves as psychiatric liaison to the New York Presbyterian Hospital/Weill Cornell Medicine (NYP/WCM) kidney transplant service and is chief of psychiatry at the Hospital for Special Surgery.

At NYP/WCM, Dr Barnhill has directed the inpatient psychiatric consultation team, served as departmental vice chair for consultation-liaison psychiatry, directed mental health services for all NYP/WCM house staff, and served as psychiatric liaison to the heart failure service. 

Dr. Barnhill's scholarly efforts have focused on the assessment and treatment of people who present with some combination of sadness, anxiety, stress, substance use, burnout, comorbid medical conditions, and relationship issues.

Dr. Barnhill's 7 books include: DSM-5-TR Clinical Cases (2023), which is the case-based guide to American psychiatry's primary diagnostic manual; Approach to the Psychiatric Patient, 2nd edition (2019), a text that includes over 100 authors who are faculty members at Weill Cornell Medicine or Columbia University; and Co-Occurring Mental Illness and Substance Use Disorders: A Guide to Diagnosis and Treatment, edited with Dr. Jonathan Avery (2017). These books have been translated into a total of 12 languages. 

Dr. Barnhill has served on the editorial board for books published by the the American Psychiatric Association. Dr. Barnhill writes the Anxiety, Stress, and Trauma section for the online Merck Manual.

Dr. Barnhill chairs the WCM psychiatry department's Appointments and Promotions Committee. Dr. Barnhill serves on the WCM medical student Promotions and Graduation Committee.  He has served on NYP/WCM's Ethics Committee for over 20 years and has chaired the WCM General Faculty Council (the representative body for all WCM faculty) and the Payne Whitney Faculty Council.

He has been a member of the department's Council on Diversity, Equity, and Inclusion (DEI) since its inception in 2019; he also serves on the DEI Council's subcommittee on Recruitment and Retention. 

Outside of NYP/WCM, Dr. Barnhill chairs the Ethics Committee for the Columbia University Center for Psychoanalytic Training and Research, where he is on the Executive Committee. He is a member of the Institutional Review Board at Rockefeller University.

Since 2015, Dr. Barnhill has directed the psychiatry section of the annual Salzburg-Weill Cornell Seminars through the Open Medical Institute.  He has served on the WCM Faculty Committee for the Weill Bugando Medical College in Mwanza, Tanzania and on the International Psychoanalytic Association's and the American Psychiatric Association's Committees to the United Nations and on the United Nations Commission on the Status of Women. 

Dr. Barnhill has lectured or consulted throughout the country, as well as the Middle East, Africa, Europe, and Asia.

Dr. Barnhill has maintained a private psychiatric practice throughout his career.