GenRED cases (N = 1,020) were recruited from multiple clinical settings and media and internet announcements and advertisements. Cases were assessed with the Diagnostic Interview for Genetic Studies19 (DIGS, version 3; http://nimhgenetics.org) and consensus best estimate diagnoses were assigned by review of DIGS, informant report and available psychiatric records.4 Probands had recurrence (two or more episodes, or one episode lasting at least three years), onset before age 31, and recurrent MDD in a sibling or parent with onset before age 41 (but no suspected bipolar-I disorder in a sibling or parent), features which predict greater familial liability to MDD.3, 20, 21 The GenRED GWAS used the same MGS controls as STAR*D (see above). GAIN-MDD recruited individuals from a twin registry and two population-based samples in the Netherlands, selecting cases who received MDD diagnoses based on a Composite International Diagnostic Interview (CIDI), and controls without MDD and without high neuroticism scores.5 Each study excluded bipolar disorder, schizophrenia or schizoaffective disorder and more severe substance use disorders, with minor differences in exclusion criteria.
