Objective: Sluggish cognitive tempo (SCT) symptoms uniquely contribute to psychiatric and functional outcomes in child samples; however, the psychometric properties of SCT measures among adult outpatients are unknown. Method: Adults (n = 124) presenting for an ADHD evaluation provided self- and collateral report of SCT symptoms. Results: The SCT scale had good internal consistency and yielded three factors across raters: Slow/Daydreamy, Sleepy/Sluggish, and Low Initiation/Persistence. SCT scores exhibited convergent validity with ADHD symptoms across raters. Individuals with ADHD received higher SCT ratings than those without ADHD via collateral report, a pattern that was similar when comorbidity was considered. SCT was associated with poorer functioning after accounting for ADHD symptoms with some differential effects based on reporting source. Conclusion: Findings support the internal consistency and validity of a three-factor SCT scale among adult outpatients. Differential results between self- and collateral report demonstrate the importance of multiple reporters of SCT in clinical settings.
Keywords: ADHD; functional outcomes; psychiatric outpatients; psychometrics; sluggish cognitive tempo.