Sleepy, sluggish, worried, or down? the distinction between selfreported sluggish cognitive tempo, daytime sleepiness, and internalizing symptoms in youth with attention-deficit/hyperactivity disorder

Sluggish cognitive tempo (SCT) consists of symptoms of slowness, sluggishness, daydreaming, and low motivation. SCT has been linked to attention-deficit/hyperactivity disorder (ADHD), internalizing symptoms, and daytime sleepiness. Although there is clear evidence that SCT and ADHD symptoms are distinct constructs, the distinction between SCT, anxiety/depression, and daytime sleepiness is less clear. Prior research has largely relied upon parent-report to evaluate potential overlap between SCT, sleep, and anxiety/depression, despite best practice suggesting that self-report should be used to assess internalizing symptoms. The present study used adolescent self-report to evaluate whether SCT was distinct from daytime sleepiness, anxiety, and depression. Participants were 285 middle school students comprehensively diagnosed with ADHD. Ten confirmatory factor analyses were conducted: four 1-factor models, three 2-factor models, one 3-factor model, one 4-factor model, and a higher order model. Results showed that SCT was indeed distinct from all tested constructs, with the four-factor model including self-report of SCT, anxiety, depression, and daytime sleepiness meeting adequate model fit criteria. All models including SCT as its own factor had improved model fit over models with SCT in a combined factor with another construct. Implications for the assessment and treatment of SCT are discussed.