Initial childhood screening included teacher reports on the Inattention/Overactivity scale of the IOWA Conners Rating Scale (Pelham, Milich, Murphy & Murphy, 1989), parent reports on the Child Behavior Checklist (CBCL; Achenbach, 1991), and structured interview of a parent using the Diagnostic Interview Schedule for Children (Shaffer, Fisher, Dulcan, Davies, Piacentini, Schwab-Stone, Lahey, Bourdon, Jensen, Bird, Canino & Regier, 1996). The attention problems subscale from the CBCL was used as the primary clinical measure for this study. Participants recruited prior to 1994 were diagnosed using DSM-III-R criteria for ADHD and tested using the Wechsler Intelligence Scale for Children, Revised Edition (WISC-R) (Wechsler, 1974); those recruited after 1994 were evaluated using DSM-IV criteria and tested using the third edition of the WISC (WISC-III) (Wechsler, 1991). Subgroups recruited before and after 1994 did not differ significantly on any parent or teacher rating. Psychosis, autism, neurological disorders, or IQ below 70 was exclusionary at baseline.
