My research program aims to improve our understanding of the etiology of health risk factors with the goal of preventing disease and reducing the population burden of ill health, and my focus is four-fold.

First, I study the genetics and epidemiology of obesity and smoking, and lead the Developmental Genetic Epidemiology of Smoking project combining data from twin registers worldwide to map the changing role of genetic and environmental factors to smoking stages across the lifespan.

Second, I manage phenotypic and genotypic data sharing from the Virginia Twin Study of Adolescent Behavioral Development study with genomewide association study consortia, to identify genes for substance use and psychiatric disorders, and apply related genomic approaches.

Third, I collaborate with researchers in Sweden and Norway, capitalizing on their large population registries to identify familial and individual risk factors for substance use and mental health outcomes with family- and genome-based approaches, focusing on inter-generational genetic and cultural transmission.

Fourth, I explore individual differences in substance use and abuse trajectories and related phenotypes in terms of the combined effects of unmeasured and measured genes and environment in the nationwide Adolescent Brain Cognitive Development Study. These projects rely on my expertise in structural equation modeling of data on twins, extended families, and genotypes, to investigate the causes of (co)variation and test developmental and causal genetic epidemiological hypotheses.