Table 3. Distribution of allele repeat numbers of the 40-bp VNTR in the DAT1 3′ UTR and 48-bp VNTR region in exon 3 of DRD4 .

Genetics findings	SCT w/o ADHD (n=31)	SCT + ADHD (n=67)	ADHD w/o SCT (n=146)	TH (n=92)	p-value	Cohen's w index	Group comparisons
DRD4 genotype
At least one 7R allele	9 (29)	15 (22.4)	14 (9.6)	14 (15.2)	0.014	0.178	ADHD < SCT
4R/4R	15 (48.4)	37 (55.2)	97 (66.4)	44 (47.8)	0.023	0.168	TD < ADHD
DAT1 genotype
10R homozygosity	19 (61.3)	35 (52.2)	77 (52.7)	33 (35.9)	0.025	0.167	None

Data are presented as n (%).

ADHD = attention-deficit/hyperactivity disorder; bp = base pair; DAT1 = dopamine transporter gene; DRD4 = dopamine D4 receptor gene; SCT = sluggish cognitive tempo; TD = typically developing controls; UTR = untranslated region; VNTR = variable-number tandem repeats.