Table 3.

Peer included studies for children with ADHD.

Design	Treatment condition	Participants N	Age Years (mean ± SD)	Inclusion criteria	Outcome measurea	Treatment outcome
Abikoff et al. [53] RCT: random assignment ADHD peer intervention	1 year weekly, 2nd year monthly (1) mph only (2) mph + MPT + SST (3) mph + ACT	mph: 34 (ADHD) mph + MPT: 34 (ADHD) mph + ACT: 35 (ADHD)	8.2 ± 0.8	ADHD diagnosis Positive response to mph	Social skills outcomes: SSRS: parent + child form Others: TOPS: teacher form Observations in gym	SSRS: significant improvement TOPS: significant improvement Significantly fewer positive and negative behaviours
Choi and Lee [54] RCT: random assignment ADHD peer intervention	Weekly EMT and SST treatment for 16 weeks (1) EMT group (2) SST group (3) Waitlist control	EMT: 25 SST: 25 Control: 24	EMT: 11.0 ± 0.9 SST: 11.1 ± 0.9 Control: 10.8 ± 0.8	ADHD diagnosis Total WISC-Revised Korean Version IQ > 90 Behaviour Problem Scale score in clinical range on CBCL	Social skills outcomes: Peer Relational Skills Scale Others  Emotion Expression Scale for Children Child Depression Inventory State-Trait Anxiety Inventory for Children	No differences between SST and control groups. EMT group improved significantly more than control EMT group improved significantly more than SST and control groups SST group improved significantly more than control group, but no differences between EMT and control groups
Frankel et al. [55] QES: child and parent manually assigned Non-ADHD peer intervention	SST weekly for 12 weeks (1) Treatment (2) Waitlist control	Treatment 35: ADHD/14: no ADHD Waitlist control 12: ADHD/12 no ADHD	9.05 ± 3.06	Peer problems ADHD (using mph) ODD based on DSM-III-R	Social skills outcomes: SSRS: parent form; attention and self-control subscales Others: PEI: teacher form	SSRS: significantly greater improvement PEI: nonsignificant improvement on the withdrawal scale. Significant improvement on the aggression scale
Guli et al. [56] QES: children manually assigned ADHD and other diagnosis peer interventions	SST weekly for 12 weeks or twice weekly for 8 weeks (1) SCIP group (2) Clinical control	SCIP: 18 (5 ADHD/2 NLD/11 ASD) Control: 16 (3 ADHD/6 NLD/7 ASD)	10.97 ± 1.98	ADHD diagnosis Overall intelligence > 80 on WISC-III	Social skills outcomes: BASC: parent form; withdrawal and social skills subscales DANVA2 Observed social interaction SSRS: parent form Others: Parent and child interviews	BASC: no significant effects found DANVA2: no significant effects found Observations: medium effects for increases in positive interactions and decreases in solitary play for treatment group Baseline measure for presence of clinically significant social skills deficits 75% reported one or more specific positive changes
Haas et al. [57] QES: children manually assigned Non-ADHD peer intervention	Behavioural treatment for 8 weeks in the context of a STP (1) Treatment (2) Control	Treatment 54: ODD or CP/ADHD Control 16: no ODD or CP/ADHD	9.48 ± 1.58	ADHD diagnosis Nonmedicated	Social skills outcomes: SIRF: staff observations Peer sociometric interviews Others: Time-out measures	SIRF: significant improvement in social skills and problem solving Peer sociometrics: significant improvement in Likert and Dislike nominations Time-out: significant improvements
Hannesdottir et al. [58] RCT: random assignment ADHD peer intervention	Behavioural and SST treatment with working memory training (1) Treatment (2) Waitlist control (3) Parent training	Treatment: 16 Control: 14 Parent training: 11	9.2 ± 0.62	ADHD diagnosis	Social skills outcomes: SSRS: parent form Others: ADHD Rating Scale-IV ERC SDQ Icelandic WISC-IV	Significant group × time interactions favouring treatment group over waitlist control Significant group × time interactions favouring treatment group over waitlist control for inattention, but not hyperactivity/impulsivity No significant main effect of time No significant main effect of time Significant main effects on two subscales (Coding and Letter-Number Sequencing), but no significant group × time interactions
Hantson et al. [59] QES: child and parent manually assigned ADHD peer intervention	SST daily for 2 weeks in the context of an intensive therapeutic summer day camp (1) Treatment (2) Treatment as usual control	Treatment 33: ADHD Treatment as usual control 15: ADHD	8.6 ± 1.6	ADHD diagnosis IQ > 70 on WISC-III	Social skills outcomes: IPR: child form WFIRS-P: parent form Others: CGI-P: parent form	IPR: significant improvement WFIRS-P: Significant improvements except for WFIRS Risky Activities subscale CGI-P: significant improvement
Huang et al. [60] QES: child and parent manually assigned ADHD peer intervention	Weekly SST treatment for 8 weeks consisting of 80-minute sessions (1) SST group (2) No treatment control	SST: 45 Control: 52	SST: 8.2 ± 0.9 Control: 8.5 ± 0.9	ADHD diagnosis	Social skills outcomes: SSRS: child + teacher form Others  SNAP: parent + teacher CBCL: child form	SSRS-C: significant improvement in Self-Control in favour of SST group; SSRS-T: significant improvement in active participation in favour of SST group SNAP-P: main effect of group on Oppositional subscale; SNAP –T: Main effect of group on Active Participation subscale CBCL-C: main effect of group on Anxious/Depressed subscale
Jensen et al. [61] RCT: random assignment 3-year follow-up ADHD peer intervention	Treatment over 14 months (1) Medication only (2) Behavioural treatment incl. parent training + STP + school-based treatment (3) Combined incl. medication + behavioural treatment (4) Community care control	Medication management 115: (ADHD) Behavioural treatment 127: (ADHD) Combined treatment 127: (ADHD) Community care control 116: (ADHD)	11.8 ± 0.95	Children who participated in the 1999 MTA study	Social skills outcomes: SSRS: parent + teacher forms Others: SNAP: parent + teacher forms WIAT: reading score CIS	SSRS: effect size for improvement from baseline to 36 months across all treatment groups was 0.8–0.9 SNAP: effect size for improvement from baseline to 36 months across all treatment groups was 1.6–1.7 for ADHD and 0.7 for ODD WIAT: effect size for improvement from baseline to 36 months across all treatment groups was 0.1–0.2 CIS: effect size for improvement from baseline to 36 months across all treatment groups was 0.9–1.0
Kolko et al. [62] QES: children manually assigned ADHD and other diagnosis peer interventions	3 weekly sessions for 5 weeks (1) SCST group (2) SA group	SCST: 36 (10 ADHD/11 CD/15 OD) SA: 20 (4 ADHD/12 CD/4 OD)	10.4 ± 2.1	Score of at least 7 on a four-item social problems screen, with at least one maximum rating	Social skills outcomes: CAI-M: Self-report LNS-M: Self-report SPS: Staff report Sociometric Ratings: Staff Peer Nomination Behavioural Role-Play In vivo behavioural observations	CAI-M: significant improvement in post-training scores LNS-M: SCST group showed significant reduction in post-training scores SPS: SCST group showed significant reduction in posttraining scores Both groups improved significant SCST group showed greater pre-post reduction nominations SCST group showed significant improvement SCST group exhibited significant improvement
Mikami et al. [63] RCT: random assignment Typically developing peer intervention	Weekdays for four weeks total Weekdays for 2 weeks per treatment allocation (1) MOSAIC then COMET (2) COMET then MOSAIC	MOSAIC: 12 ADHD/58 TD COMET: 12 ADHD/55 TD	8.15 ± 0.79	ADHD diagnosis after screening IQ >80 on WASIl	Social skills outcomes: Peer sociometric nominations Peer interaction observations Messages from peers Others: Teacher-Child Rating Scale subscales of problem behaviours	Main effect on positive nominations for treatment was not significant. Received fewer negative nominations and more reciprocated friendship nominations when in MOSAIC relative to COMET group No main effect for treatment condition Received a significantly greater proportion of positive messages when in MOSAIC relative to COMET group No main effects for treatment condition
MTA Cooperative Group [64] RCT: random assignment ADHD peer intervention	Treatment over 14 months (1) Medication only (2) Behavioural treatment incl. parent training + STP + school-based treatment (3) Combined incl. medication + behavioural treatment (4) Community care control	Medication management 144: (ADHD) Behavioural treatment 144: (ADHD) Combined treatment 145: (ADHD) Community care control 146: (ADHD)	8.5 ± 0.8	ADHD combined type diagnosis In residence with the same primary caretaker(s) for last 6 months or longer	Social skills outcomes: SSRS: parent + teacher Others: SNAP: parent + teacher MASC: child form Parent-child relationship questionnaire WIAT: (reading, math + spelling)	SSRS: significant improvement for parent-reported internalizing problems for combined treatment over behavioural treatment SNAP: combined + medication management were clinically and statistically superior to behavioural treatment + community care MASC: improvements of small magnitude Improvements of small magnitude Significant improvement for reading achievement score for combined treatment over behavioural treatment
MTA Cooperative Group [65] RCT: random assignment 24-month follow-up ADHD peer intervention	Treatment over 14 months (1) Medication only (2) Behavioural treatment incl. parent training + STP + school-based treatment (3) Combined incl. medication + behavioural treatment (4) Community care control	Medication management 128: (ADHD) Behavioural treatment 139: (ADHD) Combined treatment 138: (ADHD) Community care control 135: (ADHD)	8.4 ± 0.8	Children who participated in the 1999 MTA study	Social skills outcomes: SSRS: parent + teacher Others: SNAP: parent + teacher Negative/ineffective discipline factor WIAT: (reading, math + spelling)	SSRS: nonsignificant overall treatment effect SNAP: significant overall treatment effect Nonsignificant overall treatment effect WIAT: nonsignificant overall treatment effect
Pfiffner et al. [66] RCT: random assignment ADHD and other diagnosis peer interventions	Treatment over 12 weeks First cohort: (1) CLAS program (2) Waitlist control Second-Fifth cohort: (1) CLAS program (2) Treatment as usual control	Five cohorts of children randomized to either CLAS program or control 25: ADHD, 2: Undifferentiated Attention Deficit Disorder; 19: Oppositional Defiant Disorder, 3: Conduct Disorder, 4: Separation Anxiety Disorder, 5: Overanxious Disorder, 2: Dysthymic Disorder.	8.7 ± 1.2	ADHD diagnosis IQ > 80 on the WASI Attending school full time with school consenting to participate in school-based treatment	Social skills outcomes: SSRS: parent + teacher Others: Child Symptom Inventory SCT Scale COSS: parent + teacher Test of Life Skill Knowledge Clinical Global Impressions: parent + teacher	SSRS: significant improvements Significant reductions in number of DSM-IV inattention symptoms SCT: significant treatment effects COSS: significant improvements of organisational skills Significantly improvements Significantly greater improvement
Shechtman and Katz [67] RCT: random assignment ADHD and other diagnosis peer interventions	Weekly for 15 weeks (1) Group therapy (2) Waitlist control	Group Therapy: 42 (20: ADD or ADHD/22 LD) Waitlist control: 45 (14 ADD or ADHD/31 LD)	13.26 ± 0.77	ADD/ADHD or LD diagnosis	Social skills outcomes: Adolescent Interpersonal Competence Questionnaire Intimate Friendship Scale Working Alliance Inventory	Significant treatment condition by time effect Nonsignificant treatment condition by time effect High association between bonding with group members and gains on social competence
Storebø et al. [68] RCT: random assignment ADHD peer intervention	Weekly for 8 weeks (1) Experimental treatment incl. SST + parent training + standard treatment (2) Standard treatment alone	Experimental treatment 28: ADHD Standard treatment alone 27: ADHD	10.4 ± 1.31	ADHD diagnosis IQ > 80 Not previously medicated	Indexes from Conners 3 and Connors CBRS: Social skills outcomes: Social Problems score Peer Relations score Others: Executive Functions score Academic score Aggressiveness score Emotional score Hyperactivity score	No statistically significant difference when comparing groups Neutral result between groups Neutral result between groups Neutral result between groups Highly significant changes towards fewer symptoms No statistically significant difference when comparing groups
Waxmonsky et al. [69] RCT: random assignment ADHD peer intervention	Weekly for 8 weeks (1) Atomoxetine + BT (2) Atomoxetine alone	Atomoxetine + BT 29: ADHD Atomoxetine alone 27: ADHD	8.59 ± 1.58	ADHD diagnosis IQ > 75 Positive response to atomoxetine	Social skills outcomes: SSRS: parent + teacher Others: Student Behaviour Teacher Response Observation Code DBD: parent + teacher APRS: teacher PSERS: parent + teacher CDRS-R: child + parent interview DRC/ITBE Clinical Global Impressions Scale: clinician	SSRS: significantly lower parent-rated problem behaviours No difference between groups post-treatment DBD: marginally significant improvement of ADHD and ODD symptoms APRS: significantly higher teacher-rated impulse control PSERS: mean scores well within the mild range. Marginally lower depression scores post-treatment. Suicidal thoughts decreased significantly over time but with no difference between groups DRC/ITBE: Significant main effect of medication/time 51.9% of subjects in Atomoxetine-only and 55.2% of Atomoxetine + BT subjects were rated as much or very much improved

Notes. RCT = randomized controlled trial, QES = quasi-experimental study, mph = methylphenidate, MPT = Multipsychosocial Treatment, SST = social skills training, ACT = attention control treatment, ADHD = Attention-Deficit Hyperactivity Disorder, SSRS =Social Skills Rating Scale [70], TOPS =Taxonomy of Problem Situations [71], EMT = emotional management training, WISC-Revised Korean Version = Wechsler Intelligence Scale for Children-Revised Korean Version [72], CBCL = Child Behaviour Checklist [73, 74], ODD = oppositional defiant disorder, DSM-III-R = Diagnostic and Statistical Manual of Mental Disorders 3rd Edition, PEI = Pupil Evaluation Inventory [75], SCIP = Social Competence Intervention Program, NLD = nonverbal learning disorder, ASD = autism spectrum disorder, WISC-III (Weschler Intelligence Scale for Children-III [76]), BASC = Behaviour Assessment System for Children [77], DANVA2 = Diagnostic Analysis of Nonverbal Accuracy 2 Nowicki, 2004, CP = conduct problems, SIRF = Staff Improvement Rating Form [78], ERC = Emotion Regulation Checklist [79]; SDQ = Strengths and Difficulties Questionnaire [80], Icelandic WISC-IV = Wechsler Intelligence Scale for Children-Icelandic version [81], IPR = Index of Peer Relations [82], WFIRS-P = Weiss Functional Impairment Rating Scale-Parent Version [83], CGI-P = Conners' Global Index-Parent Version [84], SNAP = (Swanson, Nolan, and Pelham Rating Scale [85], STP = summer treatment program, MTA = Multimodal Treatment Study of Children with ADHD, WIAT = Wechsler Individual Achievement Test [86], CIS = Columbia Impairment Scale [87], SCST = social-cognitive skills training, SA = social activity group, CD = conduct disorder, OD = other disorders, CAI-M = Children's Assertiveness Inventory-Modified [88], LNS-M = Loneliness Scale for Children-Modified [89], SPS = Social Problems Screen, MOSAIC = Making Socially Accepting Inclusive Classrooms, COMET = contingency management training, TD = typically developing, WASI = Wechsler Abbreviated Scale of Intelligence [90], MASC = Multidimensional Anxiety Scale for Children [91], CLAS = Child Life and Attention Skills program, SCT Scale = Sluggish Cognitive Tempo Scale [92], COSS = Children's Organizational Scale [93], DSM-IV = Diagnostic and Statistical Manual of Mental Disorders 4th Edition, LD = learning disabilities, Conners 3 [94], Conners CBRS = Conners Behaviour Rating Scales [94], BT = behaviour therapy, DBD = Disruptive Behaviour Disorders Rating Scale [95], APRS = Academic Performance Rating Scale [96], PSERS = Pittsburgh Side Effects Rating Scale [97], CDRS-R = Children's Depression Rating Scale-Revised [98], and DRC/ITBE = Daily Report Card/Individual Target Behaviour Evaluation. ^aWhen handling studies with multiple social skills outcome measures, one singular outcome measure was chosen that most comprehensively reflected the construct social skills. This singular outcome measure was then used for the calculation of an effect size. No measures were aggregated within the study to obtain one effect size.