. 2020 Jan 14;10:2983. doi: 10.3389/fpsyg.2019.02983

Table 4.

Results of included studies.

	Study	Effect sizes		Main findings
1	Azami et al. (2016)	CPT (total correct): d = 1.12 Raven's progressive matrices: d = 1.436 Backward digit span: r = −0.721(placebo); r = −0.11 (medication) SNAP-IV (ADHD-PHI): d = 1.784	Span board: d = 1.34 Forward digit span: r = −0.567 (placebo); r = −0.037 (medication) SNAP-IV (ADHD-C): d = 1.422	For simple EF tasks (e.g., sustained attention and inhibition), the experimental group had the same results as the active stimulant medication group. However, for a number of complex EFs (e.g., verbal and visuospatial short-term memory and non-verbal reasoning), the experimental group showed better results than the active stimulant medication and placebo groups.
2	Beck et al. (2010)	ADHD index: d = 0.76 Cognitive problems/inattention: d = 0.79 Hyperactivity: d = 0.36 DSM-IV inattentive scale: d = 1.49 BRIEF Teacher Scale Initiate: d = 0.42	BRIEF Parent Scale Metacognition index: d = 0.91 Working memory: d = 0.85 Initiate: d = 0.94 Plan\|organize: d = 0.92	The experimental group showed better results on parent ratings of overall ADHD symptoms, inattention, initiation, planning/organization, and working memory than the waitlist control group.
3	Bigorra et al. (2016)	Working memory composite score: d = 0.81 CPT (detectability): d = 0.60 BRIEF Parent Scale Working memory: d = −0.86 Plan\|organize: d = −0.71 Metacognition index: d = −0.78 ADHD symptom composite Parents: d = −0.39 Teachers: d = −0.69	CPT (commission errors): d = 0.40 BRIEF Teacher Scale Initiate: d = −0.55 Working memory: d = −0.36 Monitor: d = −0.72 Shift: d = −0.39 Metacognition: d = −0.37 School learning behavior (WFIRS-P): d = −0.86	The experimental group improved significantly more than the control group on parent ratings of the metacognition index (i.e., the child's ability to monitor, initiate, plan, organize, and sustain future-oriented problem solving in working memory). Also, the experimental group improved significantly more than the control group on teacher ratings of the metacognitive index, initiation, working memory, monitoring, and shifting. Also, for the experimental group compared to the control group there were significant improvements in performance-based measures of EF, ADHD symptoms, and functional impairment.
4	Capodieci et al. (2018)	Forward digit span: d = 0.72 Backward digit span: d = 1.70 Selective working memory: d = 1.70	Walk-No walk: d = 1.25 MF-14: d = 1.29	The experimental group showed better results than the control group in performance-based measures of working memory and other neuropsychological measures. Effects were not found for inattention and hyperactivity problems rated by teachers and parents.
5	Davis et al. (2018)	Test of Variables of Attention Attention Performance Index: d = 0.35 Attention Performance Index (high severity): d = 0.71	Reaction Time Mean (high severity): d = 0.65 Reaction Time Variability (high severity): d = 0.62	The experimental group showed more improvements than the control group on performance-based measures of attention, working memory, and inhibition than the control group, especially among children with greater symptom severity and impaired attention.
6	Dovis et al. (2015)	Corsi Block Tapping Test Forward: $η_{p}^{2} =$ 0.16 Backward: $η_{p}^{2} =$ 0.09		Only children in the full-active condition (where working memory, inhibition, and cognitive flexibility were trained) compared to a partially-active condition (where only inhibition and cognitive flexibility were trained) and to a placebo condition showed better results on measures of visuospatial short-term memory and working memory.
7	Egeland et al. (2013)	CPT (Processing speed): η² = 0.105		The experimental group presented better results than the control group only in processing speed. Reading and mathematics were improved in the experimental group, changes in ADHD symptom rating scales were not visible. In addition, the improvements in reading scores remained significant 8 months later.
8	Green et al. (2012)	—		The experimental group presented reductions in off-task ADHD-associated behaviors after training. Improvements in working memory performance-based measures were also found. No significant improvements were found on parent rating scales.
9	Hannesdottir et al. (2017)	ADHD-RS-IV (Parent) Inattention: d = 0.90 Hyperactivity\|Impulsivity: d = 0.74 Strengths and Difficulties Questionnaire Total score: d = 0.75	Social Skills Rating System Total score: d = 0.54 Emotion Regulation Checklist Emotion regulation: d = 0.67	Compared to a waitlist control group, the experimental group (OutSMARTers Program) showed a reduction of ADHD symptomatology, improved social skills and better emotion regulation according to parents. No improvements were found on performance-based measures. No differences were found between the experimental and a parent training group, as both groups showed some improvement. These improvements were still visible 3 months later.
10	Johnstone et al. (2012)	—		Children in both experimental groups (i.e., working memory and inhibitory control training with and without attention monitoring) showed significant improvements in ratings of ADHD symptomatology according to parents and other family members. Better performance in tasks pertaining to spatial working memory, ignoring distracting stimuli, and sustained attention were also reported, with the attention monitoring via EEG retaining little effect on the outcomes. The follow-up sessions carried after a 6-week interval revealed maintenance of gains.
11	Menezes et al. (2015)	—		The experimental group showed better performance on measures of attention/inhibition and auditory working memory compared to the control group. No effect was found for measures of more complex executive functions, such as flexibility, visual working memory, and verbal fluency. Parent rating scales showed no improvement of ADHD symptomatology or executive functioning.
12	Minder et al. (2018)	Conners-3 ADHD DSM-IV indices (Parent) Inattention: η² = 0.096		Both experimental groups (cognitive training vs. neurofeedback) improved in ratings of ADHD symptomatology and executive functions according to parents and teachers and off-task behavior as reported by blinded raters. An effect of training was found for cognitive training only on inattention symptoms rated by parents.
13	Qian et al. (2017)	—		After the intervention, children in the experimental group were rated by parents as displaying improved executive functioning, diminished ADHD symptomatology, reduced risk-tasking behaviors and enhanced academic performance. Despite these improvements, the experimental group was still distinguishable from the healthy control group in almost all variables.
14	Re et al. (2015)	Walk-No walk: $η_{p}^{2}$ = 0.27	MF-14 (errors): $η_{p}^{2}$ = 0.37	Children with ADHD presented better performance in tasks assessing attention, inhibition, and working memory. Improvements in children with typical development who attended the training were also found. Both parents and teachers' ratings of ADHD symptomatology improved for the experimental and control groups.
15	Shuai et al. (2017)	—		The experimental group presented better performance in neuropsychological tests after the intervention, with improvements in processing speed, inhibition, shifting, working memory, and planning. Results from parent rating scales showed reduced ADHD symptomatology and behavioral problems as well as improved executive functioning and academic performance. At post-test, there were no significant differences between the ADHD and healthy control groups.
16	Steiner et al. (2014)	—		Only children who attended the neurofeedback intervention showed significant improvement in ratings of attention, executive functioning and off-task behavior compared with those in the control and cognitive training conditions.
17	Steiner et al. (2011)	Conners Rating Scales-Revised Inattention: d = 0.80 ADHD index: d = −0.70	Behavior Assessment Scales for Children −2 Attention Problems: d = −0.80 Behavior Rating Inventory of Executive Function Global Executive Composite: d = −0.60	The experimental group that received Neurofeedback training was rated by parents as presenting less symptoms of ADHD and improved behavior. Parents of children that attended the Standard Computer Format training reported less inattention and ADHD symptoms as well as improvements in executive functioning. Teacher and self-report ratings did not show symptomatology improvements.
18	Tamm et al. (2013)	SNAP-IV (Parent) Inattention: d = 1.65 Hyperactivity\|Impulsivity: d = 0.65 SNAP-IV (Clinician) Inattention: d = 1.41 Hyperactivity\|Impulsivity: d = 0.68 Behavior Assessment Scales for Children−2 Attention Problems (parent): d = 0.66 Clinical Global Impressions Severity: d = 1.04 Improvement: d = 1.14	D-KEFS Tower time per move ratio: d = 0.55 BRIEF Parent Scale Shift: d = 0.63 Initiate: d = 0.98 Working memory: d = 1.16 Planning: d = 1.00 Organization: d = 0.53 Monitor: d = 0.70 Behavioral Regulation Index: d = 0.63 Metacognition Index: d = 1.13 General Executive Composite: d = 1.03	After the intervention, the experimental group performed significantly better on a measure of planning compared to a waitlist control group. No effects were found in the remainder performance-based measures. Parents rated children in the experimental group as presenting fewer ADHD symptoms and better executive functioning. Clinician ratings of ADHD symptoms presented reduced scores and children reported a better ability to focus and shift attention. Teacher ratings did not reach statistical significance.
19	Tamm and Nakonezny (2015)	BRIEF Parent Scale Shift: d = 1.01 Emotion Regulation: d = 0.97	SNAP-IV (Clinician) Inattention: d = 1.10	No improvements were found in performance-based measures of executive functions for the experimental group compared to the waitlist control group following the intervention. However, parents of children in the experimental group reported effects on the shift and emotion regulation subscales of the BRIEF. Blinded clinicians' ratings revealed decreased inattention symptoms.
20	van der Donk et al. (2015)	Creature counting (correct): d = 0.26 Word list interference (remember): d = −0.33 BRIEF Teacher Scale Metacognition Index: d = −0.07	Span board: d = 0.85 Comprehension of instructions: d = −0.08 BRIEF Parent Scale Behavioral Regulation Index: d = −0.05 Metacognition Index: d = 0.01	Both experimental groups (Cogmed working memory training vs. Pay Attention in Class) improved on measures of attention, inhibition, and planning. Parent and teacher ratings of executing functioning and ADHD symptomatology presented decreased scores, but no effects were found on academic, behavioral, and quality of life outcomes.
21	van der Oord et al. (2014)	Disruptive Behavior Disorder Rating Scale Inattention: η² = 0.25 Hyperactivity\|Impulsivity: η² = 0.22	BRIEF Parent Scale Metacognition Index: η² = 0.16 Global Executive Composite: η² = 0.16	The experimental group showed better results on parent ratings of ADHD symptomatology as well as on the metacognition index and total score of the BRIEF compared to a waitlist control group. These effects maintained stable at the 9-week follow-up and improvements on inhibition were found. Teacher ratings showed no effects of training at post-test but revealed improvements from pre-test to follow-up on ADHD symptomatology.
22	van Dongen-Boomsma et al. (2014)	—		No significant treatment effect was found on the outcome measures applied. The experimental and placebo groups did not differ at the end of the intervention on behavioral symptoms, neurocognitive performance, executive and global functioning.