Margaret (Peg) McCarthy received a Ph.D. from the Institute of Animal Behavior at Rutgers University, completed postdoctoral training at Rockefeller University and was a National Research Council Fellow at NIH-NIAAA before joining the faculty of the University of Maryland School of Medicine in 1993. She was professor in the Department of Physiology before becoming the chair of the Department of Pharmacology in 2011, in which capacity she served until 2024.

McCarthy has a long-standing interest in the cellular mechanisms establishing sex differences in the brain. She uses a combined behavioral and mechanistic approach in the laboratory rat to understand both normal brain development and how these processes might go selectively awry in males versus females. McCarthy is the inaugural Director of the University of Maryland – Medicine Institute for Neuroscience Discovery (UM-MIND), a fellow with AAAS and ACNP and former President of the Organization for the Study of Sex Differences and the Society for Behavioral Neuroendocrinology. She was elected to the National Academy of Medicine in 2024.