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Specific genetic tests exist for phenotypes associated with large genetic deletions (e.g., genotype X0 in Turner syndrome) or duplications (e.g., trisomy 21 in Down syndrome). Smaller copy number variations (CNVs) are mostly benign and more common (an estimated 12% of normal newborns have deletions, and 2% have duplications). Two new studies examine CNVs associated with psychiatric illness.
Guilmatre and colleagues compared the mean number of CNVs at 28 loci in three diagnostic groups (schizophrenia, 236 patients; mental retardation, 247; autism spectrum disorders, 260) and in a group of 236 healthy controls; the loci were selected from a Medline search. The disease groups had significantly higher percentages of CNVs (4.2%–6.2%) than the con…