The study medication will consist of identical capsules filled Concerta® over-encapsulated to preserve double-blinding. The weekly dosages will be low, medium, and high based on weight cut-offs. Participants weighing less than 25kg will receive 18mg (low), 27mg (medium), and 36mg (high) dosages and participants weighing above 25kg will receive 18mg (low), 36mg (medium), and 54mg (high) dosages during the 3-week upward titration trial. Weekly ratings monitoring behavioral and side effect symptoms score and the Pittsburgh Side Effects Rating Scale.

The study medication will consist of identical capsules filled with an inert white power (placebo). Weekly ratings monitoring behavioral and side effect symptoms score and the Pittsburgh Side Effects Rating Scale.

Changes in symptom ratings were assessed on the Vanderbilt ADHD parent rating scales (VADPRS). A measure of ADHD symptom severity (Total Symptom Score [TSS]) is computed by totaling the scores from items 1-18 (Inattentive +Hyperactive-impulse domains), with a rating of none=0, occasionally=1, often=2, very often=3, provided. Scores for inattentive and hyperactive-impulsive domains were generated by totaling the 9 symptoms in these domains, and a TSS was computed by totaling items across domains.

The Behavior Rating Inventory of Executive Functioning (BRIEF)-Parent was used to assess executive functioning behaviors. The global executive composite (GEC), behavior regulatory index (BRI), and metacognitive index (MI) T-scores were used, with higher scores reflecting poorer executive functioning. T-scores were normalized to 50 with a standard deviation of 10.

The Wechsler Intelligence Scale for Children, 4th Edition Processing Speed Index (WISC-IV-PSI) has been designed for children 6-16:11 years of age and provides a measure of processing speed. For this index scale, the average score is 100 with a standard deviation of 15. Higher scores reflect better processing speed. One participant was administered the Wechsler Adult Intelligence Scale 4th Edition Processing Speed Index (WAIS-IV-PSI). All scores were included in the combined WISC/WAIS processing speed variable since both measures yield highly correlated standard scores.

For the first week, participants received the low-dose Methylphenidate condition (Concerta® over-encapsulated). Over the subsequent 3 weeks, the dose was titrated based on medication response and side effects to determine the optimal dose used for week 4. At the end of week 4, participants crossed-over and repeated the same procedures for the placebo condition. No wash-out period was used.

The weekly dosages were low, medium, and high based on weight cut-offs. Participants weighing less than 25kg will receive 18mg (low), 27mg (medium), and 36mg (high) dosages and participants weighing above 25kg will receive 18mg (low), 36mg (medium), and 54mg (high) dosages during the 3-week upward titration trial.

Changes in symptom ratings were assessed on the Vanderbilt ADHD parent rating scales (VADPRS). A measure of ADHD symptom severity (Total Symptom Score [TSS]) is computed by totaling the scores from items 1-18 (Inattentive +Hyperactive-impulse domains), with a rating of none=0, occasionally=1, often=2, very often=3, provided. Scores for inattentive and hyperactive-impulsive domains were generated by totaling the 9 symptoms in these domains, and a TSS was computed by totaling items across domains.

All participants who completed outcome data and full cross-over intervention

For the first week, participants received the low-dose Methylphenidate condition (Concerta® over-encapsulated). Over the subsequent 3 weeks, the dose was titrated based on medication response and side effects to determine the optimal dose used for week 4.

The weekly dosages were low, medium, and high based on weight cut-offs. Participants weighing less than 25kg will receive 18mg (low), 27mg (medium), and 36mg (high) dosages and participants weighing above 25kg will receive 18mg (low), 36mg (medium), and 54mg (high) dosages during the 3-week upward titration trial.