After applying quality control filters, association with ADHD was tested with 835,136 SNPs in 735 DSM-IV-TR ADHD trios from 732 families; clinical demographics of the sample are presented in Table 2. Subjects recruited at WASH-U were older (p<0.001) and more likely to be diagnosed with predominantly inattentive ADHD (p<0.001) compared with both the MGH and the UCLA samples. Subjects recruited at UCLA were less likely to be Caucasian compared with both the MGH and WASH-U samples (p<0.001). Thus, pooled sample was predominantly Caucasian, male, 12 years of age on average with roughly equal prevalence of combined-type and predominantly inattentive-type ADHD (Table 2).
