The sample included 1,530 patients with a lifetime diagnosis of MDD and 1,700 screened healthy controls. All cases were drawn from NESDA. Presence of DSM-IV lifetime diagnosis of MDD was assessed using the Composite Interview Diagnostic Instrument (CIDI, version 2.1)(24) administered by specially trained research staff at baseline or one of the biannual follow-up assessments. From NESDA, 316 healthy controls were also selected, including participants without any lifetime psychiatric disorder. The majority of controls (n=1,384) were drawn from NTR participants who had no reports of MDD, no known first-degree relatives with MDD and a low factor score based on a multivariate analyses of depressive complaints, anxiety, neuroticism and somatic anxiety(25). Case-control selection criteria in the present study are the same as previously applied to include NESDA and NTR participants in the Genetic Association Information Network (GAIN) MDD dataset(25), which was used in previous studies(26–29) including the largest MDD GWAS available to date by the Psychiatric Genomics Consortium(4). Of note, 1,452 cases and 99 controls from the current study were previously included in the larger (1,943 cases, 1,807 controls) GAIN-MDD dataset.
