Study | Design | N | Mean age, yr | Stimulation protocol | Outcome measures | |||||
---|---|---|---|---|---|---|---|---|---|---|
Anode/cathode | mA | Sessions, n | Timing* | Duration, min | Clinical† | Cognitive† | ||||
Children | ||||||||||
Bandeira et al.51‡ | Open-label | 9 | 11 | Left dlPFC/right SOA | 2 | 5 | Online | 28 | PGI-I | Visual Attention Test (TAVIS-3; omission errors [+]); NEPSY-II-inhibition (switch errors [+]); digit span task; Corsi cube task |
Breitling et al.67 | Single-blind, sham-controlled, crossover | 21 | 14 | Right IFC/left cheek | 1 | 1 | Online | 20 | Not tested | Flanker task (incongruent trials: errors [+]¶,** and ICV [+]¶,††) |
Left cheek/right IFC | 1 | 1 | Online | 20 | Not tested | Flanker task | ||||
Munz et al.60 | Double-blind, sham-controlled, crossover | 14 | 12 | Left dlPFC/right cheek; right dlPFC/left cheek | 0.25 | 1 | Offline | 25 (5 on, 1 off) | Not tested | Go/no-go task (go RT [+] and intrasubject RTV [+]); motor memory task; alertness task |
Nejati et al.68 (experiment 1) | Double-blind, sham-controlled, crossover | 15 | 10 | Left dlPFC/right dlPFC | 1 | 1 | Offline | 15 | Not tested | Go/no-go task; n-back (accuracy, RT [+]); Stroop task (incongruent trials: errors [+] and RT [+]); WCST (completion time [+]) |
Nejati et al.68 (experiment 2) | Double-blind, sham-controlled, crossover | 10 | 9 | Left dlPFC/right SOA | 1 | 1 | Offline | 15 | Not tested | Go/no-go task; n-back (accuracy [+],¶ RT [+]**); WCST (total categories completed [+], total errors [+], perseverative errors [+])** |
Right SOA/left dlPFC | 1 | 1 | Offline | 15 | Not tested | Go/no-go task (no-go accuracy [+])**; n-back; WCST (total categories completed [+], total errors [+] and perseverative errors [+]¶)** | ||||
Prehn-Kristensen et al.61 | Double-blind, sham-controlled, parallel | 12 | 12 | Left dlPFC/right cheek; right dlPFC/left cheek | 0.25 | 1 | Offline | 25 (5 on, 1 off) | Not tested | Declarative memory task (accuracy [+]); alertness task; digit span task |
Soff et al.62 | Double-blind, sham-controlled, crossover | 15 | 14 | Left dlPFC/vertex | 1 | 5 | Online | 20 | FBB-ADHD (inattention [+])‡‡,§§,¶¶ | QbTest (inattention [+]††; hyperactivity [+]***)§§,¶¶ |
Soltaninejad et al.64 | Single-blind, sham-controlled, crossover | 20 | 16 | Left dlPFC/right SOA | 1.5 | 1 | Online | 15 | Not tested | Go/no-go task (go accuracy [+])¶,**; Stroop task |
Right SOA/left dlPFC | 1.5 | 1 | Online | 15 | Not tested | Go/no-go task (no-go accuracy [+])¶,†††; Stroop task | ||||
Soltaninejad et al.43§ | Single-blind, sham-controlled, crossover | 20 | 16 | Right IFC/left SOA | 1 | 1 | Online | 15 | Not tested | Go/no-go task (go accuracy [+]); Stroop task |
Sotnikova et al.63 | Double-blind, sham-controlled, crossover | 13 | 14 | Left dlPFC/vertex | 1 | 1 | Online | 20 | Not tested | QbTest (RT [+], RTV [+],‡‡‡ omission errors [−], accuracy [−])§§§ |
Adults | ||||||||||
Allenby et al.65‡ | Double-blind, sham-controlled, crossover | 37 | 32 | Left dlPFC/right SOA | 2 | 3 | Online | 20 | Not tested | Conners’ CPT (commission errors [+]¶¶¶); stop task |
Cachoeira et al.74 | Double-blind, sham-controlled, parallel | Active: 9 Sham: 8 | Active: 31 Sham: 34 | Right dlPFC/left dlPFC | 2 | 5 | Offline | 20 | ADHD checklist (inattention [+], total [+])****; SDS (after tDCS only [+]) | Not tested |
Cosmo et al.66 | Double-blind, sham-controlled, parallel | Active: 30 Sham: 30 | Active: 32 Sham: 33 | Left dlPFC/right dlPFC | 1 | 1 | Offline | 20 | Not tested | Go/no-go task |
Jacoby et al.42 | Single-blind, sham-controlled, crossover | 20 | 23 | Left and right dlPFC/cerebellum | 1.8 | 1 | Offline | 20 | Not tested | CPT (multi-button presses [+]) |
ADHD = attention deficit/hyperactivity disorder; CPT = continuous performance task; dlPFC = dorsolateral prefrontal cortex; FBB-ADHD = parents’ version of a German adaptive diagnostic checklist for ADHD; ICV = intrasubject coefficient of variation; IFC = inferior frontal cortex; NEPSY-II = Neuropsychological Development Assessment, Second Edition; PGI-I = Patient Global Impression of Improvement; QbTest = Quantitative Behaviour Test; RT = reaction time; RTV = reaction time variability or standard deviation of reaction times; SDS = Sheehan Disability Scale; SOA = supraorbital area; Stroop = Stroop colour and word task; tDCS = transcranial direct current stimulation; WCST = Wisconsin Card Sorting Task.
↵* Refers to whether cognitive performance was during stimulation (online) or after stimulation (offline).
↵† Plus sign [+] = statistically significant improvement; minus sign [−] = statistically significant impairment.
↵‡ Combined stimulation with cognitive training.
↵§ Originally published in Persian; translated by the lead author (ZS).
↵¶ Would likely not survive multiple comparison correction.
↵** Comparisons between stimulation conditions based on post-hoc least significant difference tests, which do not correct for multiple comparisons.
↵†† Based on underpowered analysis focusing on the first session, with 7 participants per condition.
↵‡‡ Improvement seen only 7 days after the fifth anodal tDCS session.
↵§§ Did not survive correction for multiple comparisons.
↵¶¶ Based on underpowered analysis focusing on the first 5 sessions, with 7/8 participants per condition.
↵*** Improvement seen immediately after the fifth anodal tDCS session and 7 days later.
↵††† Significant in comparison to cathodal tDCS only.
↵‡‡‡ Based on a crossover interaction; tDCS reduced RT and RTV in 1 of 4 conditions (2-back tasks), but this did not survive correction for multiple comparisons.
↵§§§ Included carryover effect raised by Soff et al.62
↵¶¶¶ Significant only immediately after anodal tDCS; not significant 3 days later.
↵**** Inattention improved immediately after anodal tDCS and after 2 weeks; total score improved only after 2 weeks.