Table 2
(a) Characteristics of between-group studies (age and percentages only for ADHD groups with treatment (Tx)): research design and participants

1st author (date)Research designAge (y/o)N of ADHD, HC, Tx, and WL/no/other Tx% males% ADHD subtypes% medication status% comorbid disorders

Bachmann (2018) [13]RCT, pre/post18-65, , 40, 0, 21, 1938, 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/post18-45, , 43, 17, 29, 3154.5n.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, 62, 0, 49, 1354, , 61.22 (MPH), 24.49 (other)46.94 (MDD, BD, AD, SD, BPD)
Edel (2017) [32]N-RCT, WL, pre-post, 91, 0, 39, 5259, 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, 33, 0, 17, 1658.8, (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-up19-24, , 54, 0, 28, 2657.1, 28.6 (MPH), 42.8 (other), 28.6 (none)n.r.
Hepark (2019) [45]RCT, WL18-65, , 103, 0, 55, 4838CAARS-INV: ,
CAARS-SR: ,
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-up18+, , 120, 0, 60, 6047, , 6038 (MDD/Sx), 2 (BD), 13 (AD), 70 (Somato), 2 (ED), 2 (dysthymia)
Mitchell (2017) [25]WL & treatment group, pre-post18-50, , 20, 0, 11, 945.5, 54.5 (“stimulants”)54.5
Schoenberg (2014) [12]RCT, WL, pre-post19-53, , 50, 0, 26, 2437.5n.r.38 (MPH), 24 (other), 38 (none)n.r.

(1) Statistics and design: n.r. = nonreported; y/o = years old;  = mean;  = 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.
(b) Characteristics of between-group studies: intervention

1st author (date)InterventionIntervention lengthTherapistInformants

Bachmann (2018) [13]MAP or PE2.5 h/week, 8  h+daily home practicen.r.Self, objective
Bueno (2015) [44]MAP or no intervention2.5 h/week, 8  h+daily home practiceHighly experienced practitionersSelf, objective
Cole (2016) [40]DBT (+elements of mindfulness) or CBT modules (impulsivity/hyperactivity, attention)2 h individual psychotherapy+group/week, 12-month  h+homework assignmentsNurses, psychologists, and psychiatrists, trained in DBT+CBTSelf
Edel (2017) [32]MBT (+mindfulness component of DBT) or ST (DBT-oriented skills training)2 h/week, 13  hExperienced psychologist working with ADHD+5 y experience in DBT/MBTSelf, expert-rated scale
Fleming (2015) [35]DBT (+elements of mindfulness) or skills handouts1.5 h group/week, 8  h+7 10 min individual coaching/week+90 min group (1st week follow-up)Group leader (A.P.F.), coleader (L.R.M.), graduate students in clinical psychology with DBT training & intervention, psychologist with experience in ADHD studentsSelf, objective
Gu (2018) [48]MBCT1 h individual/week, 6  h+30 min self-practice/day workbook psychoeducationGroup leader, psychiatrist specializing in ADHD+8 y experience, MBCT trainers, psychologist with experience in ADHD studentsSelf, objective
Hepark (2019) [45]MBDT (+PE)12-week meditation exercises built up gradually+home practice 30 min/dayPsychiatrist specializing in ADHD (10 y), mindfulness teacher (S.H.) & nurse specialist, Association of Mindfulness-Based Teachers, 150 h education (MBSR)/MBCTSelf, investigator
Janssen (2019) [50]MBDT (+PE)2.5 h group/week, 8  h+6 h silent day+home practice 30 min/dayMindfulness teachers at different levels of competenceSelf, objective
Mitchell (2017) [25]MAP2.5 h/week, 8  h+home practicePh.D. clinical psychologySelf, objective
Schoenberg (2014) [12]MBCT3 h/week, 12  h+30-45 min self-practice/dayPsychiatrist specializing in ADHD with 9 y training in MBCTSelf, objective

Intervention: CBT = cognitive behavioral therapy; DBT = dialectical behavior therapy; MAP = mindful awareness program; MBT/MBCT = mindfulness-based training; PE = psychoeducation; ST = skills training.
(c) Characteristics of between-group studies: measure of outcome

1st author (date)ADHD symptomsCognitive/executive functionEmotional disturbanceQuality of lifeAcademic performanceMindfulness

Bachmann (2018) [13]CAARS-SR/OR-backn.r.n.r.n.r.n.r.
Bueno (2015) [44]ASRSANT, CPT-2BDI, STAI-T, PANAS-XAAQoLn.r.n.r.
Cole (2016) [40]ASRS v1.1, BIS-11n.r.BDI-II, BHS, STAXIWHOQoL-BREF, QFSn.r.KIMS
Edel (2017) [32]DSM-IV-(SR/OR)n.r.WRIGSESn.r.MAAS
Fleming (2015) [35]BAARS-IV, BADDSCPT-2BAI, BDI-IIAAQoLGPAFFMQ
Gu (2017) [48]CAARS-S:SVANTBAI; BDI-IIVASGPAMAAS
Hepark (2019) [45]CAARS-INV, CAARS-SRBRIEF-ASRBDI-II-NL, STAIOQ 45.2n.r.KIMS
Janssen (2019) [50]CAARS-INV:SV, CAARS-S: SVBRIEF-An.r.OQ 45.2, MHC-SFn.r.FFMQ-SF, SCF-SF
Mitchell (2017) [25]Current ADHD Symptom ScaleDEFS, BRIEF-A, ANT, CPT, DST, TMT, WAIS-RDERS, DTSn.r.n.r.n.r.
Schoenberg (2014) [12]CAARS-S:SVCPT-Xn.r.OQ 45.2n.r.KIMS

(2) ADHD symptoms: ASRS (v1.1) = Adult ADHD Self-Report Scale; BAARS-IV = Barkley Adult ADHD Rating Scale-IV; BADDS = Brown ADD Rating Scales; BIS-11 = 11th version of the Barratt Impulsiveness Scale; CAARS-S:SV = Conners’ Adult ADHD Self-Rating Scale; CAARS-SV = Conners’ Adult ADHD Rating Scales-Screening Version; CAARS-SR = self-report version of the Conners’ Adult ADHD Rating Scale; CAARS-INV = investigator rating version of the Conners’ Adult ADHD Rating Scale; DSM-IV-(SR/OR) = Diagnostic and Statistical Manual of Mental Disorders, 4th Edition (self-rating/other-rating). (2) Cognitive/executive function: ANT = Attention Network Task; BRIEF-A = Behavior Rating Inventory of Executive Functioning-Adult Version; BRIEF-ASR = Behavior Rating Inventory of Executive Function-Adult Self-Report version; CPT-2 = the Conners’ Continuous Performance Test-2nd edition; CPT-X = visual Continuous Performance Task; DEFS = Deficits in Executive Functioning Scale; DST = Digit Span Test (WAIS-R); TMT = Trail Making Test; WAIS-R = Wechsler Adult Intelligence Scale-Revised. (3) Emotional disturbance: BAI = Beck Anxiety Inventory; BDI-II/BDI-II-NL = Beck Depression Inventory (2nd edition); BHS = Beck Hopelessness Scale; DERS = Difficulties in Emotion Regulation Scale; PANAS-X = Affect Schedule-Expanded form; STAI = State-Trait Anxiety Inventory; STAXI = State-Trait Anger Expression Inventory; WRI = Wender–Reimherr Interview. (4) Quality of life: AAQoL = Adult ADHD Quality of Life Questionnaire; GSES = Generalized Self-Efficacy Scale; MHC-SF = Positive Mental Health Short Form; OQ 45.2 = Outcome Questionnaire; QFS = questionnaire of social functioning; VAS = Visual Analog Scale (personal health status); WHOQoL-BREF = World Health Organization Quality of Life. (5) Mindfulness: MAAS = Mindful Attention Awareness Scale; FFMQ = Five Facet Mindfulness Questionnaire; KIMS = Kentucky Inventory of Mindfulness Skills; SCF-SF = Self-Compassion Short Form. (6) Academic performance: GPA = Grade Point Average.