(a) Characteristics of between-group studies (age and percentages only for ADHD groups with treatment (Tx)): research design and participants

1st author (date)	Research design	Age (y/o)	N of ADHD, HC, Tx, and WL/no/other Tx	% males	% ADHD subtypes	% medication status	% comorbid disorders
Bachmann (2018) [13]	RCT, pre/post	18-65, $\overline{x}=40$, s = 10.58	40, 0, 21, 19	38	C = 81, I = 19	None (3 months before and during the study)	14 (AD), 57 (Sx), 4 (OC), none (Schizo, BD, SD, AU, SUI/SI, ND, Somato)
Bueno (2015) [44]	N-RCT, pre/post	18-45, $\overline{x}=31.2$, s = 7.5	43, 17, 29, 31	54.5	n.r.	69.7 (MPH)	n.r.
Cole (2016) [40]	ADHD-treated vs. ADHD-WL at baseline, post, 3-month and 6-month follow-up, end of treatment	$\overline{x}=36.6$, s = 10.02	62, 0, 49, 13	54	C = 73.5, I = 22.5, H = 5	61.22 (MPH), 24.49 (other)	46.94 (MDD, BD, AD, SD, BPD)
Edel (2017) [32]	N-RCT, WL, pre-post	$\overline{x}=33.8$, s = 10.1	91, 0, 39, 52	59	C = 69.2, I = 30.8	43.6 (MPH), 38.5 (other)	25.6 (BPD), 30.8 (other PD), 17.9 (social anxiety), 10.3 (MDD/Sx), 5.1 (dysthymia), 2.6 (SD)
Fleming (2015) [35]	RCT, baseline, post, 3-month follow-up	$\overline{x}=21.2$, s = 1.67	33, 0, 17, 16	58.8	C = 5.9, I = 88.2 + 5.9 (4 (Sx))	29.4 (MPH), 41.2 (other), 29.4 (none)	AD, MDD/Sx (% n.r.)
Gu (2018) [48]	RCT, ADHD-treated vs. ADHD-WL pre-post, 3-month follow-up	19-24, $\overline{x}=20.2$, s = 1.03	54, 0, 28, 26	57.1	C = 6.3, I = 93.3	28.6 (MPH), 42.8 (other), 28.6 (none)	n.r.
Hepark (2019) [45]	RCT, WL	18-65, $\overline{x}=36.5$, s = 10	103, 0, 55, 48	38	CAARS-INV: I = 5.2, H = 5.8 CAARS-SR: I = 4.3, H = 5.1	46 (MPH), 15 (other), 40 (none)	n.r.
Janssen (2019) [50]	RCT, ADHD-MBCT+TAU vs. ADHD-TAU, baseline, post, 3-month and 6-month follow-up	18+, $\overline{x}=39.7$, s = 11.1	120, 0, 60, 60	47	C = 50, I = 38, H = 8	60	38 (MDD/Sx), 2 (BD), 13 (AD), 70 (Somato), 2 (ED), 2 (dysthymia)
Mitchell (2017) [25]	WL & treatment group, pre-post	18-50, $\overline{x}=40.55$, s = 6.83	20, 0, 11, 9	45.5	C = 27.3, I = 72.7	54.5 (“stimulants”)	54.5
Schoenberg (2014) [12]	RCT, WL, pre-post	19-53, $\overline{x}=39.5$, s = 9.5	50, 0, 26, 24	37.5	n.r.	38 (MPH), 24 (other), 38 (none)	n.r.

(1) Statistics and design: n.r. = nonreported; y/o = years old; $\overline{x}$ = mean; s = standard deviation; HC = healthy control; N-RCT = nonrandomized control trial; RCT = randomized control trial; Tx = treatment; WL = waiting list. (2) ADHD subtypes: ADHD = Attention-Deficit and Hyperactivity Disorders; I = inattentive; H = hyperactive; C = combined. (3) Comorbid disorders: AD/Sx = anxiety disorder or symptoms; AU = autism; BD = bipolar disorder; BPD = borderline personality disorder; ED = eating disorder; MDD/Sx = major depressive disorder or symptoms; ND = neurological disorders; OC = obsessive compulsive disorders. (4) PD = any personality disorder; Somato = somatoform disorder; SD = substance dependence; SUI\SI+suicidality: self-injurious behavior. MPH = methylphenidate.