Fig. 1.

Overview of Participant Recruitment Fig. 1 illustrates the participant flow into this study using a case-finding, best-estimate procedure. On the left top moving to the right, the primary Oregon-ADHD-1000 cohort was recruited through widespread public outreach and mass mailings and then screened to find cases of ADHD and non-ADHD typically developing youth who met study inclusion criteria. “Other” represents cases in which only one reporter rated notable symptoms, or the case was subthreshold/NOS (e.g. 4 symptoms with impairment), or the child was taking a disqualifying medication (e.g.anti-depressant) at baseline. The same procedure was used for the generalizability sample named the Michigan-ADHD-1000 (not depicted to maintain readability; described below). On the bottom left to right, the ASD cohort (also described later in the text) was recruited from hospital records and then diagnostic status was confirmed by a similar best-estimate multi-clinician review procedure as used in the ADHD-1000. Please refer to the main text for full details on recruitment and diagnosis.