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Editor’s note: Copy number variants (CNVs) refer to an important type of genetic variation. CNVs arise as a result of misalignment of homologous chromosomes during meiosis, and result in segments of DNA being duplicated or deleted. CNVs can be large (usually defined as ≥1 megabase) or small, and have been found to have an important role in conferring risk for neurospsychiatric disease.