The Helsinki Birth Cohort Study (HBCS) is composed of 8 760 individuals born between the years 1934-1944 in one of the two main maternity hospitals in Helsinki, Finland. Between 2001 and 2003, a randomly selected sample of 928 males and 1 075 females participated in a clinical follow-up study with a focus on cardiovascular, metabolic and reproductive health, cognitive function and depressive symptoms. In 2004, various psychological phenotypes were assessed, including the NEO personality dimensions. There were 1 443 subjects with both valid phenotype and genotype data (59.8% women). The mean age of the subjects was 63.4 (SD=3). The mean age of the men was 63.3 (SD=3) and of the women was 63.5 (SD=3). Detailed information on the selection of the HBCS participants and on the study design can be found elsewhere.40-42
