Dr. O'Neill completed her undergraduate degree in psychology and pre-professional studies at the University of Notre Dame, her medical school degree at the Johns Hopkins University School of Medicine, a general pediatrics residency at Lurie Children's Hospital in Chicago, and a neurodevelopmental disabilities combined residency/fellowship at the Kennedy Krieger Institute and Johns Hopkins Hospital in Baltimore, MD. She is board certified in both General Pediatrics and Neurology with special qualifications in Child Neurology. She enjoys practicing medicine in a multidisciplinary environment where providers and therapists collaborate to optimize care and help all children with disabilities to meet their full developmental potential.

As the Director of the Lurie Children's Down syndrome clinic, Dr. O'Neill's main research interest lies in better characterizing the medical, neurologic, developmental, and behavioral profiles of children with Down syndrome and exploring interventions and therapeutic strategies that might ultimately benefit these individuals and their families. Additionally, she is collaborates with other specialists to determine neurodevelopmental profiles and natural histories in children with rare epilepsies and other neurogenetic syndromes or neurodevelopmental disabilities.

Dr. O'Neill's clinical time is split between both the division of developmental and behavioral pediatrics and the division of child neurology at Lurie Children's Hospital. She is the director of the Lurie Children's Down syndrome clinic through the DBP division, which is her primary area of interest. Additionally, she specializes in the care of individuals with developmental delay, intellectual disability, autism spectrum disorder, learning disabilities, ADHD, cerebral palsy, and a variety of neurobehavioral and neurogenetic disorders. She is capable of adeptly managing both the developmental and neurologic aspects of care for these individuals in a comprehensive manner.