NESDA is a longitudinal, multi-site, naturalistic, case-control cohort study following a sample of around 3,000 participants with and without depressive and/or anxiety disorders from the Netherlands. The original NESDA sample of 2,981 participants (2,329 individuals with and 652 individuals without a lifetime diagnosis of depressive and/or anxiety disorders) were recruited from the community, primary care practices and specialised mental health institutions in the regions of Amsterdam and Leiden, and in the provinces of Groningen, Drenthe and Friesland. The sample were initially assessed at baseline between 2004 and 2007, and subsequently followed up for 13 years with 7 waves of extensive assessments. At the 9-year follow-up (wave 6), the study recruited additional participants who were siblings of 256 original NESDA participants with a lifetime anxiety and/or depressive disorder.