The enrichment of large, rare CNVs was greatest in the children with ADHD and intellectual disability, in whom the average number of CNVs per patient was 5·69 times higher (p=2·0×10−6) than that in the control group (table 1). 12 (36%) children with ADHD and intellectual disability carried a CNV larger than 500 kb, compared with 38 (11%) of those without intellectual disability. Nevertheless, despite a significant difference in the rates of CNVs in the children with ADHD with and without intellectual disability (p=0·00099, two-tailed test), large, rare CNVs were still significantly enriched by 1·68 times (p=0·0077) in those without intellectual disability (n=319, mean IQ=89) when compared with the control group (table 1). Irrespective of the presence or absence of intellectual disability, children with ADHD had a significant excess of both deletions and duplications (table 1). Finally, when genomic DNA was available for both parents, we examined the inheritance of each large, rare CNVs (12 ADHD probands without intellectual disability). Of 15 CNVs, four were de novo, six were inherited from the mother, and five from the father (webappendix p 2).
