GPC participants were primarily recruited from populations in eight US states: California sites at the University of Southern California, University of California at Los Angeles, Cedars Sinai Medical Center, and University of California at Irvine; Georgia sites at Emory University and Georgia Regents University; Massachusetts sites at various Department of Mental Health and community clinics; New York sites at New York University, State University of New York at Stony Brook, and State University of New York, Upstate Medical University Syracuse; North Carolina site at University of North Carolina at Chapel Hill; Texas sites at Texas Tech University in El Paso and San Antonio; and Ohio site at Wright State University. Each GPC study site team consists of a site coordinator, field interviewers, and certified phlebotomists.
