Table 2.
Neuropsychological test performance of patients with ADHD and the control group
| Variables | CG | ADHD-OFF | ADHD-ON | Omnibus test (Kruskal–Wallis) | Pairwise group comparisons | |||
|---|---|---|---|---|---|---|---|---|
| (n = 80) | (n = 53) | (n = 31) | CG vs. ADHD-OFF | CG vs. ADHD-ON | ADHD-OFF vs. ADHD-ON | |||
| M ± SD | M ± SD | M ± SD | χ2 (df) | p | Cohen’s r | Cohen’s r | Cohen’s r | |
| Basic cognitive functions | ||||||||
| Processing speed (Z score) a | − .77 | − .23 | ||||||
| Tonic alertness (RT) | 245 ± 44 | 271 ± 59 | 249 ± 38 | 8.76 (2) | .013 | – | – | – |
| Phasic alertness (RT) | 243 ± 45 | 260 ± 56 | 243 ± 32 | 4.69 (2) | .096 | – | – | – |
| Vigilance (RT) | 566 ± 117 | 722 ± 189 | 639 ± 154 | 25.93 (2) | < .001* | .44* | .21 | .20 |
| Distractibility (Z score) a | − .80 | − .22 | ||||||
| Tonic alertness (SD) | 38 ± 24 | 55 ± 33 | 38 ± 20 | 13.61 (2) | .001* | .31* | .04 | .27* |
| Phasic alertness (SD) | 41 ± 22 | 48 ± 27 | 37 ± 15 | 4.10 (2) | .128 | – | – | – |
| Vigilance (SD) | 111 ± 51 | 176 ± 82 | 144 ± 99 | 23.67 (2) | < .001* | .42* | .15 | .25 |
| Vigilance (omissions) | 1.01 ± 1.67 | 2.53 ± 3.70 | 1.83 ± 3.09 | 8.26 (2) | .016 | – | – | – |
| Higher order cognitive functions | ||||||||
| Executive functions (Z score) a | − .55 | − .20 | ||||||
| Interference (quotient) | 2.62 ± .50 | 2.79 ± .63 | 2.56 ± .54 | 3.69 (2) | .158 | – | – | – |
| Planning (score) | 20.78 ± 6.16 | 11.68 ± 5.86 | 15.36 ± 7.01 | 49.38 (2) | < .001* | .60* | .33* | .24 |
| Cognitive flexibility (quotient) | 2.48 ± .75 | 2.64 ± .81 | 2.37 ± .67 | 2.53 (2) | .282 | – | – | – |
| Verbal fluency (# correct) | 23.16 ± 6.29 | 20.79 ± 6.08 | 23.68 ± 6.35 | 4.76 (2) | .093 | – | – | – |
| Working memory (# correct) | 7.24 ± 2.11 | 6.49 ± 1.84 | 6.26 ± 1.57 | 7.38 (2) | .025 | – | – | – |
| Memory (Z score) a | − .80 | − .51 | ||||||
| Immediate recall (# correct) | 32.55 ± 6.13 | 23.68 ± 6.48 | 23.97 ± 6.16 | 55.37 (2) | < .001* | .58* | .51* | .09 |
| Delayed recall (# correct) | 29.01 ± 7.30 | 20.21 ± 7.02 | 20.32 ± 6.84 | 45.39 (2) | < .001* | .52* | .46* | .09 |
| Immediate recognition (% correct) | 83.37 ± 10.26 | 76.53 ± 12.43 | 81.24 ± 9.84 | 9.21 (2) | .010 | – | – | – |
| Delayed recognition (% correct) | 75.04 ± 12.28 | 67.31 ± 9.71 | 72.68 ± 11.46 | 13.85 (2) | .001* | .32* | .08 | .23 |
| Visuospatial memory (# correct) | 20.04 ± 5.83 | 20.20 ± 6.60 | 25.00 ± 5.46 | 17.03 (2) | < .001* | .03 | .38* | .38* |
| Source memory (# correct) | 79.34 ± 13.89 | 69.27 ± 15.55 | 73.63 ± 15.79 | 12.78 (2) | .002* | .31* | .16 | .13 |
| Prospective memory (score) | 12.55 ± 6.39 | 6.36 ± 4.06 | 6.19 ± 3.51 | 50.81 (2) | < .001* | .54* | .51* | .10 |
| Complex attention (Z score) a | − .69 | − .02 | ||||||
| Selective attention (omissions) | 8.71 ± 7.44 | 11.10 ± 8.61 | 9.00 ± 9.82 | 5.22 (2) | .074 | – | – | – |
| Selective attention (commissions) | .31 ± .63 | 1.15 ± 5.73 | .33 ± .76 | .05 (2) | .975 | – | – | – |
| Divided attention (omissions) | 1.15 ± 1.30 | 2.44 ± 2.62 | .80 ± 1.06 | 15.01 (2) | .001* | .27* | .11 | .39* |
| Divided attention (commissions) | 1.00 ± 1.26 | 1.12 ± 1.18 | 1.41 ± 1.61 | 1.06 (2) | .589 | – | – | – |
CG control group, ADHD-OFF patients with ADHD without methylphenidate, ADHD-ON patients with ADHD with methylphenidate treatment
Definition of sets of test measures assessing basic processes and higher order functions
Basic processes:
Processing speed Tonic alertness (RT), phasic alertness (RT), and vigilance (RT) = mean reaction time in ms of the respective attention subtest (TAP)
Distractibility Tonic alertness (SD), phasic alertness (SD), and vigilance (SD) = dispersion of reaction time in ms of the respective attention subtest (TAP). Vigilance (omissions) = number of omission errors of the vigilance test (TAP)
Higher order functions:
Executive functions Interference (quotient) = division response time Color–Word interference by response time Color–Word (Stroop Color–Word test). Planning (Score) = sum score (delayed task execution task). Cognitive Flexibility (Quotient) = division response time Trail B by response time Trail A (TMT). Verbal fluency (# correct) = number of correctly produced words (RWT). Working memory (# correct) = number of correctly repeated sequences (Digit Span Backwards test)
Memory Immediate recall (# correct) and Delayed recall (# correct) = number of correctly recalled story elements of the Logical Memory subtest (Wechsler Memory scale). Immediate recognition (% correct) and delayed recognition (% correct) = number of correctly identified words (Immediate and Delayed Recognition tests). Visuospatial memory (# correct) = sum score delayed copy (Rey-Osterrieth Complex Figure). Source memory (# correct) = number of correctly classified words (source discrimination paradigm). Prospective memory (Score) = number of initiated subtests (delayed task execution task)
Complex attention Selective attention (omissions) and selective attention (commissions) = number of omission and commission errors of the selective attention test (TAP). Divided attention (omissions) and divided attention (commissions) = number of omission and commission errors of the divided attention test (TAP)
*Statistically significant at p < .01. Pairwise comparisons were computed only for significant effects on the omnibus test: a small effect is ≥ .1, a medium effect is ≥ .3 and a large effect is ≥ .5
aComposite score calculated by averaging Z scores of test variables for each set of predictors (based on healthy controls). Negative Z scores indicate impairment as compared to the control group