For genotyping we used buccal mucosa cells collected using a cytology brush (Cytobrush plus C0012, Durbin PLC) and 2.0 ml of collection buffer in 15-mL plastic tubes. Genomic DNA was extracted according to a published protocol [24]. Determination of 5-HTTLPR genotype was performed as previously described [18]. All laboratory work was performed under the ISO 9001:2000 quality management requirements and was blinded with regard to phenotype.
