Twenty-three cohorts of the GPC were included in this study (for detailed descriptions, see Supplementary Materials Online). Seventeen cohorts originated from Europe, 4 cohorts were from the USA and 2 cohorts from Australia. Most cohorts are large epidemiological studies. Some of the cohorts focused on specific birth cohorts and/or recruited individuals of specific regions in the country (e.g. ERF, VIS, KORCULA, NBS, LBC1921, LBC1936 and HBCS), or targeted twins and their family members (QIMR cohorts, NTR, MCTFR, STR, Finnish Twin Cohort). Three cohorts were designed to include cases and controls for Nicotine dependence, Alcoholism or Mood and Anxiety disorders (respectively, COGEND, SAGE-COGA and NESDA). The data collection in some of the cohorts is longitudinal in nature.
