In a small fraction of patients with schizophrenia or autism, alleles of copy-number variants (CNVs) in their genomes are probably the strongest factors contributing to the pathogenesis of the disease. These CNVs may provide an entry point for investigations into the mechanisms of brain function and dysfunction alike. They are not fully penetrant and offer an opportunity to study their effects separate from that of manifest disease. Here we show in an Icelandic sample that a few of the CNVs clearly alter fecundity (measured as the number of children by age 45). Furthermore, we use various tests of cognitive function to demonstrate that control subjects carrying the CNVs perform at a level that is between that of schizophrenia patients and population controls. The CNVs do not all affect the same cognitive domains, hence the cognitive deficits that drive or accompany the pathogenesis vary from one CNV to another. Controls carrying the chromosome 15q11.2 deletion between breakpoints 1 and 2 (15q11.2(BP1-BP2) deletion) have a history of dyslexia and dyscalculia, even after adjusting for IQ in the analysis, and the CNVonly confers modest effects on other cognitive traits. The 15q11.2(BP1-BP2) deletion affects brain structure in a pattern consistent with both that observed during first-episode psychosis in schizophrenia and that of structural correlates in dyslexia.Little information is available on whether or how rare CNVs conferring high risk of schizophrenia and/or autism affect physiologic function of otherwise normal brains. As none of these CNVs hitherto described are fully penetrant for the diseases, and both schizophrenia and autism affect cognition, we aimed to examine the possibility that the CNVs affect cognition in control carriers, those who do not suffer either disease or intellectual disability. We based our selection of CNVs on a literature search for CNVs associated with schizophrenia and/or autism ('neuropsychiatric CNVs'); this search produced 26 CNV alleles (Supplementary Table 1) 1-3 . These CNV alleles are rare, found in 0.002% to 0.2% frequency, and cumulatively in 1.16% of our sample of 101,655 genotyped subjects, representing approximately one-third of the Icelandic population ( Supplementary Tables 1 and 2).We used the subset of genotyped subjects born before 1968, without excluding patients, to examine the association of each neuropsychiatric CNV with reproductive outcome ('fecundity'), defined simply as the number of children each subject had by age 45. After correction for multiple comparisons, three neuropsychiatric CNVs were significantly associated with fecundity (Table 1). Subjects carrying the 16p11.2 deletion or the 22q11.21 duplication show reduced fecundity, with the effect in males significantly greater than in females (P 5 0.0083 and P 5 0.029 for the difference in effect by sex for the 16p11.2 deletion and the 22q11.21 duplication, respectively). In contrast, individuals carrying the 16p12.1 deletion have more children than do controls (Table 1). Those with deletions at 15q11.2(...