A related consideration is that GWAS are designed to capture common but not rare genetic variation. Rare variants can include genetic single nucleotide variations (“SNVs” present in <1% of the population) and rare copy number variations (“CNVs,” that is, structural variations in DNA sequence that involve the duplication or deletion of thousands or more than a million base pairs). Such variants have now been shown to play a role in autism117,118 and schizophrenia119,120 and bipolar disorder,121 but to date these components of the genetic architecture of depression have been largely unexplored.
