Evaluating the construct validity of adult ADHD and SCT among college students: a multitrait-multimethod analysis of convergent and discriminant validity.

OBJECTIVE To advance our understanding of adult ADHD and sluggish cognitive tempo (SCT), the present study investigates their construct validity by exploring the nature of trait- and method-related variance in self- and parent-ratings of ADHD and SCT. METHOD Using a multitrait-multimethod (MTMM) design, response variance in college undergraduates' (n = 3,925) and a subset of their parents' (n = 2,242) ratings was decomposed into method, trait, and error-specific variance. RESULTS Global evidence for convergent and discriminant validity was supported, but parameter-level comparisons suggest that method effects, situational specificity, and ADHD's core feature--inattention--are prominent. CONCLUSION This investigation offers two important conclusions: (a) SCT appears to be a related but separate factor from ADHD; and (b) self- and parent-ratings of emerging adult ADHD exhibit low to moderate correlations and support the situational specificity hypothesis, suggesting that multiple raters should be consulted when assessing adult ADHD. Implications of these findings and recommendations for the continued study of SCT are discussed.