Geneticist Steven McCarroll is conducting groundbreaking research on the causes of mental illness. McCarroll and the scientists in his lab use human genetics, molecular biology, and engineering to create new ways of studying the human brain, reveal the ways in which genomes vary from person to person, and discover the molecular and cellular processes that underlie brain illness. Steven and his team at Harvard have linked schizophrenia to specific gene variations that recruit immune molecules into “pruning” synapses in the brain, a discovery that is leading toward new ways of thinking about the biological basis of schizophrenia and new approaches for discovering medicines. Prior to leading his lab, Steve earned his Ph.D. in neuroscience at the University of California, San Francisco. He is also currently serving as Director of Genetics for the Broad Institute’s Stanley Center for Psychiatric Research.