MGS control subjects were recruited by Knowledge Networks, Inc. (Menlo Park, CA), a survey research company, from a nationally-representative marketing panel recruited by random digit dialing methods.19 Control participants consented to anonymization and deposition of their DNA and clinical information in the NIMH repository for use in any medical research. They completed an online questionnaire including a lifetime version of the Composite International Diagnostic Interview-Short Form (CIDI-SF) for common mood, anxiety and substance use diagnoses21, supplemented by questions about schizophrenia, psychosis or bipolar disorder. After excluding those who endorsed or failed to answer these latter questions (or who were outliers in total number of items endorsed), MGS selected 2,653 European-ancestry controls who passed SNP QC. We then excluded controls who met CIDI-SF criteria for MDD, or who reported recurrent depression but missed MDD by one criterion, leaving 1,636 controls for analysis.
