TABLE 1.

Sample demographics

	MRI sample	Cognition sample
N	621	611
Age (years)	3.2–21.0 (mean = 12.4, SD = 4.8)	3.2–21.0 (mean = 12.5, SD = 4.8)
Sex	Boys = 318, girls = 303	Boys = 310, girls = 301
Self‐reported ethnicity	Hispanic/Latino = 140	Hispanic/Latino = 136
	Pacific islander = 5	Pacific islander = 4
	Asian = 88	Asian = 86
	African American = 102	African American = 100
	Native American = 31	Native American = 31
	White = 426	White = 420
Handedness	Right handed = 532	Right handed = 523
	Left handed = 60	Left handed = 60
	Mixed = 24	Mixed = 24
	Not established = 3	Not established = 3
	Not available = 2	Not available = 1
Ever diagnosed with ADHD	Yes = 48	Yes = 48
	No = 567	No = 557
	Not available = 6	Not available = 6

Note: The table shows sample demographics for the MRI sample and the cognition sample. The total ethnicity numbers exceed total sample size as several subjects identified as belonging to more than one ethnicity group.