A native New Yorker, Dr. Sumner graduated Summa Cum Laude and at the top of her class with a Bachelor's degree in Psychology from Pomona College in Claremont, California. She went on to receive her PhD in Clinical Psychology from Northwestern University in Evanston, Illinois. During graduate school, Dr. Sumner worked closely with Dr. Susan Mineka and Dr. Richard Zinbarg, two experts in the study of anxiety and mood disorders. She conducted research on the role of autobiographical memory in depression, and she received a prestigious fellowship from the National institute of Mental Health for her dissertation research on this topic. As part of her graduate work, Dr. Sumner received extensive training in administering evidence-based treatments for anxiety and mood disorders, including Cognitive-Behavioral Therapy (CBT), Dialectical Behavioral Therapy (DBT), and Interpersonal Therapy (IPT). She also taught a course on CBT through the Northwestern University School of Continuing Studies.

Dr. Sumner completed her pre-doctoral internship at the Charleston Consortium, where she gained further experience with treating anxiety and mood disorders. During internship, she specialized in the treatment of traumatic stress disorders. She received extensive training in Prolonged Exposure and Cognitive Processing Therapy, two of the leading therapies for posttraumatic stress disorder (PTSD). Dr. Sumner was the recipient of the Clinical Excellence Award for her internship class.

Upon completing her internship program, Dr. Sumner returned to New York to start an Epidemiology Merit Fellowship at the Columbia University Mailman School of Public Health. At Columbia, Dr. Sumner has pursued research on stressful experiences and their impact on emotional and physical health. She is interested in identifying who may be most vulnerable to the effects of stress and trauma, and her work incorporates genetic, neuroendocrine, physiological, and environmental predictors. Dr. Sumner has published over 25 papers in peer-reviewed journals, including Molecular Psychiatry, Biological Psychiatry, Journal of Abnormal Psychology, and Psychoneuroendocrinology.