Differential impact of trait sluggish cognitive tempo and ADHD inattention in early childhood on adolescent functioning

Background Sluggish cognitive tempo ( SCT ) is distinct from attention‐deficit/hyperactivity disorder inattention ( ADHD ‐ IN ) and concurrently associated with a range of impairment domains. However, few longitudinal studies have examined SCT as a longitudinal predictor of adjustment. Studies to date have all used a relatively short longitudinal time span (6 months to 2 years) and only rating scale measures of adjustment. Using a prospective, multi‐method design, this study examined whether SCT and ADHD ‐ IN were differentially associated with functioning over a 10‐year period between preschool and the end of ninth grade. Methods Latent state‐trait modeling determined the trait variance (i.e. consistency across occasions) of SCT and ADHD ‐ IN across four measurement points (preschool and the end of kindergarten, first grade, and second grade) in a large population‐based longitudinal sample ( N  =   976). Regression analyses were used to examine trait SCT and ADHD ‐ IN factors in early childhood as predictors of functioning at the end of ninth grade (i.e. parent ratings of psychopathology and social/academic functioning, reading and mathematics academic achievement scores, processing speed and working memory). Results Both SCT and ADHD ‐ IN contained more trait variance ( M s = 65% and 61%, respectively) than occasion‐specific variance ( M s = 35% and 39%) in early childhood, with trait variance increasing as children progressed from preschool through early elementary school. In regression analyses: (a) SCT significantly predicted greater withdrawal and anxiety/depression whereas ADHD ‐ IN did not uniquely predict these internalizing domains; (b) ADHD ‐ IN uniquely predicted more externalizing behaviors whereas SCT uniquely predicted fewer externalizing behaviors; (c) SCT uniquely predicted shyness whereas both SCT and ADHD ‐ IN uniquely predicted global social difficulties; and (d) ADHD ‐ IN uniquely predicted poorer math achievement and slower processing speed whereas SCT more consistently predicted poorer reading achievement. Conclusions Findings of this study – from the longest prospective sample to date – provide the clearest evidence yet that SCT and ADHD ‐ IN often differ when it comes to the functional outcomes they predict.