Research Interest: The use of cross-sectional and longitudinal studies of twins and families to study behavioral development, and genetic and environmental influences on behavior, personality, and health. Recent research focus on the development of behavior problems in childhood and adolescence, vulnerability to drug use, abuse, and dependence, genetics and health, and linkage and association studies of behavioral traits. Dr. Hewitt is Director of the Institute for Behavioral Genetics and Executive Editor of the journal, Behavior Genetics.