After completing post-doctoral studies in behavioral genetics as a National Science Foundation Fellow at the New York State Psychiatric Institute, Columbia College of Physicians and Surgeons, Witkin joined the Department of Psychiatry at the Mount Sinai School of Medicine in New York City where she is an Assistant Professor of Psychiatry, Assistant Professor of Obstetrics, Gynecology and Reproductive Sciences, and Director of Psychological and Wellness Services for Reproductive Medicine Associates of New York (RMANY).

She also serves as Head of Patient Services Development at Progyny and Advisory Board Member for Celmatix. She served on several boards including, The Women's Advisory Board of Harvard University's Kennedy School of Government, The Board of The City of Hope, The Doctor's Committee for Mt. Sinai Department of Ob/Gyn and Reproductive Sciences, the New York Regional Transplant Program, and the Crohn's and Colitis Foundation.