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Table 1 Demographic Characteristics of Participants

From: Interaction between lead and noradrenergic genotypes affects neurocognitive functions in attention-deficit/hyperactivity disorder: a case control study

  Patients
(n = 259)
Controls
(n = 96)
T or χ2 F p (Effect size)
Age, mean (SD) years 8.8 (2.4) 10.5 (3.0) 4.957 11.306 < .001a (0.63*)
Male, n (%) 202 (78.0) 52 (54.2) 19.531   < .001a (0.51**)
IQ, mean (SD) 105.9 (14.5) 113.3 (16.4) 4.100 1.668 < .001a (0.48*)
ADHD subtypes, n (%)
Combined 73 (28.4)     
Inattentive 98 (38.1)     
Hyperactive-impulsive 57 (22.2)     
Not otherwise specified 29 (11.3)     
ADHD Rating Scale, mean (SD)
Inattention 15.0 (5.6) 3.6 (4.0) −20.343 15.542 < .001a (2.76*)
Hyperactivity-impulsivity 10.2 (6.5) 1.7 (2.0) −17.769 88.912 < .001a (2.02*)
Total 25.2 (10.7) 5.5 (5.7) −21.239 34.852 < .001a (2.30*)
Continuous Performance Test, mean (SD)
Omission errors 65.5 (20.4) 53.5 (15.1) −5.879 33.913 < .001a (0.70*)
Commission errors 65.5 (19.2) 55.5 (15.2) −5.028 16.181 < .001a (0.58*)
Response time 55.4 (12.1) 54.4 (13.2) −0.669 0.402 .504 (0.08*)
Response time variability 63.3 (17.9) 50.8 (15.4) −6.402 10.405 < .001a (0.75*)
Stroop Color-Word Test, mean (SD)
Word reading score 44.0 (11.6) 49.0 (9.5) 0.692 3.755 < .001a (0.47*)
Color naming score 45.4 (10.9) 50.9 (9.7) 0.846 4.244 < .001a (0.53*)
Color-Word score 45.3 (12.5) 50.3 (11.9) 0.546 3.344 .001a (0.41*)
Interference score 52.5 (11.3) 49.1 (13.8) 3.067 −2.311 .021a (0.27*)
Environmental measure, mean (SD)
Lead (μg/dL)
Total 1.4 (.5) 1.3 (.5) −2.818 0.526 .005a (0.20*)
Male 1.5 (0.5) 1.4 (0.6) 0.775 0.808 .439 (0.18*)
Female 1.3 (0.5) 1.1 (0.3) 2.432 7.295 .017a (0.49*)
Genotype
DAT1, n (%)*    1.288   .525 (0.15**)
10/10 217 (83.8) 85 (88.5)    
With a 10 39 (15.1) 10 (10.4)    
Without 10 3 (1.2) 1 (1.0)    
DRD4, n (%)*    0.742   .690 (0.08**)
With 4/4 146 (56.4) 58 (60.4)    
With a 4 99 (38.2) 32 (33.3)    
Without 4 14 (5.4) 6 (6.3)    
ADRA2A MspI, n (%)*    0.470   .791 (0.03**)
C/C 30 (11.6) 12 (12.5)    
G/C 113 (43.6) 38 (39.6)    
G/G 116 (44.8) 46 (47.9)    
ADRA2A DraI, n (%)*    1.833   .400 (0.16**)
C/C 80 (30.9) 23 (24.0)    
C/T 125 (48.3) 53 (55.2)    
T/T 54 (20.8) 20 (20.8)    
  1. Note: a: Items that are still significant after the multiple comparison adjustment with the 0.05 false discovery rate threshold which have a p-value <.05
  2. ADHD attention-deficit/hyperactivity disorder, IQ intelligence quotient, SD standard deviation
  3. *Cohen’s d values (0.80 = large, 0.50 = medium, 0.20 = small effect sizes)
  4. **Cohen’s h values (0.80 = large, 0.50 = medium, 0.20 = small effect sizes)