Table 1. Sample characteristics.

Samples	N pairs	Age mean (range)	Sex: n subjects	ASD cases: n subjects	IQ full-scale mean (range)
MZ discordant for ASD diagnoses	13	14.4 y (9–20)	Male: 16 Female: 10	ASD cases: 13 ADHD cases: 6 Cases with comorbid ASD and ADHD: 5	89.2 (40–121)
MZ TD	13	15.8 y (10–18)	Male: 16 Female: 10	ASD cases: — ADHD cases: —	98.1 (81–123)
MZ quantitative discordant	54	14.9 y (8–28)	Male: 60 Female: 48	ASD cases: 29 ADHD cases: 32 Cases with comorbid ASD and ADHD: 13	96.6 (58–142)
DZ quantitative discordant	46	14.3 y (8–25)	Male: 49 Female: 43	ASD cases: 23 ADHD cases: 35 Cases with comorbid ASD and ADHD: 13	97.7 (42–138)

Abbreviations: ADHD, attention deficit hyperactivity disorder; ASD, autism spectrum disorder; DZ, dizygotic; IQ, intelligence quotient; MZ, monozygotic; TD, typically developed; y, year.