tokens: METHODS : Children with attention - deficit / hyperactivity disorder ( ADHD ; n = 282 ) , all subtypes , ages 6 to 12 years , were randomized to placebo ( n = 90 ) , immediate - release methylphenidate ( IR MPH ) 3 times a day ( tid ; dosed every 4 hours ; n = 97 ) , or OROS MPH once a day ( qd ; n = 95 ) in a double - blind , 28 - day trial .