Andrew Grotzinger is a clinical psychologist with expertise in psychiatric and cognitive genetics and the development and application of multivariate genome-wide methods to large scale genomic data sets. This includes the development of Genomic SEM, a statistical framework and open-source software package that allows for flexible modeling of multivariate genomic relationships using only summary statistics from genome-wide association studies (GWAS). In the original application, Genomic SEM was applied to investigate the shared genetic pathways across five major psychiatric disorders in a paper published in Nature Human Behaviour. Andrew has since worked closely with the Cross-Disorder Working Group of the Psychiatric Genomics Consortium to apply Genomic SEM to understand the shared genetic architecture across 8 psychiatric disorders in a publication appearing in Cell. Most recently, Andrew extended Genomic SEM to include the ability to examine multivariate functional enrichment using Stratified Genomic SEM. This allows for determining whether the genetic risk sharing across traits is largely reflected in genes expressed during certain developmental stages (e.g., pre- versus post-natal), for certain tissue types (e.g., specific brain regions), or for specific mechanistic functions (e.g., synaptic pruning). In application, Andrew used Stratified Genomic SEM to characterize sources of genetic overlap across 11 major psychiatric disorders, providing insights into the biological underpinnings of pervasive psychiatric comorbidity.