Sample characteristics for those included at baseline with valid MRIs, age, intelligence quotient, reported handedness, ADHD symptom severity, and brain ROIs, as well as scan movement ratings at baseline and follow-up and scan interval and compliance rates for those included in the analyses, divided by age and medication group^a

	Children				Adults
	Methylphenidate Hydrochloride (n =  25)		Placebo (n = 23)		Methylphenidate Hydrochloride (n = 24)		Placebo (n = 23)
	Mean	SD	Mean	SD	Mean	SD	Mean	SD
Age at baseline (yr)	11.4	0.8	11.4	0.9	28.2	4.4	29.0	5.0
Estimated intelligence quotientb	104.8	21.0	102.8	15.7	107.9	8.8	107.9	6.4
ADHD symptom severity	36.6	6.2	38.4	8.2	31.8	9.9	31.0	9.9
Proportion right-handed	0.840	0.374	0.913	0.288	0.958	0.204	0.826	0.388
Left frontal cortex thickness, Tp1 (mm)c	2.805	0.229	2.763	0.236	2.471	0.170	2.553	0.164
Right medial cortex thickness, Tp1 (mm)c	2.724	0.115	2.770	0.097	2.434	0.128	2.438	0.120
Right posterior cortex thickness, Tp1 (mm)c	2.409	0.142	2.384	0.172	2.151	0.157	2.223	0.096
Scan movement Tp1c	1.2	0.4	1.2	0.4	1.0	0.0	1.1	0.2
Scan movement Tp2d	1.3	0.5	1.2	0.4	1.1	0.2	1.0	0.0
Compliance rate percentagee	83.5	15.5	79.0	18.1	90.0	8.0	85.7	8.4
Scan interval (day)f	122.3	4.2	121.4	3.9	110.8	27.5	111.7	24.6

Note:—Tp indicates time point; Tp1, baseline time point; and Tp2, follow-up time point.

^aThere were no significant (P < .05) differences in these characteristics across participants randomized to methylphenidate or placebo treatment.

^bAvailable for 21 children and 22 adults in the placebo group and all 25 children and 22 adults in the methylphenidate group.

^cAvailable for those with scans included at baseline: 23 children and 22 adults in the placebo group and 24 children and 24 adults in methylphenidate group.

^dAvailable for those with scans included at follow-up: 23 children and 21 adults in placebo group and 22 children and 22 adults in methylphenidate group.

^eAvailable for 22 children and 21 adults in the placebo group and 20 children and 22 adults in the methylphenidate group.

^fAvailable for those included who did not drop out: 23 children and 21 adults in placebo group and 23 children and 22 adults in methylphenidate group.