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Medical Leadership

Our leaders have decades of experience and a collective goal of helping members get the best quality health care possible.

Marshall Thomas, MD, President and CEO

Marshall Thomas, M.D., president and chief executive officer, is responsible for advancing the Colorado Access corporate mission and provides executive oversight for all programs.

Dr. Thomas has been with Colorado Access for two decades, with increasing levels of executive responsibility culminating in his appointment as president and chief executive officer in 2006. Throughout his career, Dr. Thomas has worked to develop systems of care that are inclusive, responsive and create synergies between patients and providers. He is a recognized national expert on improving patient health outcomes by integrating medical and behavioral health care. Under his leadership, Colorado Access has created strong business practices, expanded its client base and reoriented internal practices to support clients and providers and strengthen the safety net. In addition to his position at Colorado Access, Dr. Thomas is a professor of psychiatry and family medicine, holds the Marisco Chair for Excellence, and is the executive director of the Helen & Arthur E. Johnson Depression Center at the University of Colorado Anschutz Medical Campus.

He is a practicing psychiatrist and has been involved in the system of care development in Colorado since 1980. Dr. Thomas earned his medical degree from Baylor College of Medicine and completed his psychiatry residency at the University of Colorado Health Sciences Center.

Alexis Giese, MD, SVP Healthcare Systems and Chief Medical Officer

Alexis Giese, M.D., senior vice president of healthcare systems and chief medical officer, provides executive oversight of enterprise-wide health strategy, clinical operations, long-term services and supports, population health, care coordination and quality management. She has served at Colorado Access since 2008.

Dr. Giese has nearly 30 years of experience in innovative service delivery leadership and as a practicing psychiatrist. Her experience includes 10 years as psychiatry consultant to the Colorado Department of Human Services’ Office of Behavioral Health, community psychiatry program consultation, and health services research. Dr. Giese earned her Bachelor of Science degree from West Virginia University and her Doctor of Medicine degree from The University of Texas Health Science Center at Houston. She completed the psychiatry residency program at Georgetown University.

Dr. Giese is also a professor in the departments of psychiatry and family medicine at the University of Colorado School of Medicine and serves as the director of community programs at the Helen & Arthur E. Johnson Depression Center at the University of Colorado Anschutz Medical Campus.

Scott Humphreys, MD, Senior Medical Director

Scott Humphreys, MD, is the senior medical director providing clinical oversight to the behavioral health programs in Denver and Northeast Colorado and oversees the utilization department at Colorado Access.

Dr. Humphreys received his medical degree from the University of Oklahoma. He completed his residency in general psychiatry at Johns Hopkins Hospital where he was the chief resident. He came to Denver for his fellowship in forensic psychiatry through the University of Colorado Denver. He is also certified in addiction medicine.

For nearly 10 years, Dr. Humphreys was an inpatient and consult-liaison psychiatrist for the HealthONE hospital system. In addition to his work at Colorado Access, Dr. Humphreys is an associate medical director at the Colorado Physician Health Program. He continues to be affiliated with the forensic psychiatry training program and maintains a small private practice.

Tyler Watlington, MD, MSPH, Medical Director

Tyler Watlington, M.D., MSPH, is the medical director for Region 3 of the Accountable Care Collaborative administered by Colorado Access.

Dr. Watlington is board certified in pediatric medicine and preventive medicine. She focuses on engaging practices from a clinical and data-driven perspective, as a way to streamline efficiencies.

She received her medical degree from the Medical College of Virginia and completed her residency in pediatrics and preventive medicine at the University of Colorado Health Sciences Center. Dr. Watlington has extensive experience working in various health clinics throughout Denver. Before Colorado Access, she held various positions at Children’s Hospital Colorado; as an attending physician as well as working to improve physician processes. She received her Bachelor of Arts degree from Dartmouth College, her Doctor of Medicine degree from Virginia Commonwealth University and her Master of Science and Public Health degree from UC Health.