Obsessive-compulsive disorder (OCD) and Tourette syndrome (TS) are neurodevelopmental disorders with significant phenotypic and genetic overlap.1,2 One promising avenue for identifying cross-disorder genetic risk factors in neurodevelopmental disorders is the study of genomic copy number variants (CNVs), segments of DNA ranging from 1 kilobase to several megabases that show deletions or duplications compared to a reference.3 The association of large, rare CNVs with neurodevelopmental disorders including autism spectrum disorders (ASD), schizophrenia, and intellectual disability (ID) has been one of the most important recent advances in psychiatric genomics.4 CNVs predisposed to these disorders overlap substantially, highlighting the cross-disorder effects of this class of genetic variation.5,6 Given this robust literature, an important, unanswered question is whether large, rare CNVs are also relevant for the genetic architecture of OCD and TS.
