The NTR/NESDA study consists of unrelated individuals from Dutch twin families registered at the Netherlands Twin Register (NTR)32 and participants from the Netherlands Study of Depression and Anxiety (NESDA).33 Individuals were selected to be genotyped as part of the Genetic Association Information Network (GAIN) initiative34, of which 1 836 served as controls (mainly from NTR) and 1 862 as cases (mainly from NESDA) in a genome-wide association study for major depressive disorder.35,36 Controls were selected for absence of an MDD diagnosis and/or a low genetic liability for MDD. In this study, 3 540 individuals (65.6% women) were included with valid NEO personality and GWA data. The mean age of participants was 44.1 years (SD=13). Men were slightly older (M=46.6 years; SD=13) than women (M=42.8 years; SD=13). Personality data from NTR participants were collected in 200437 and from NESDA participants between 2004-2007.33
