A Cross-Sectional and Longitudinal Investigation of the External Correlates of Sluggish Cognitive Tempo and ADHD-Inattention Symptoms Dimensions Maria del Mar Bernad & Mateu Servera & Gloria Grases & Susana Collado & G. Leonard Burns # Springer Science+Business Media New York 2014 Abstract The objective was to determine if the external cor- relates of sluggish cognitive tempo (SCT) and ADHD- inattention (IN) dimensions were the same in cross-sectional and longitudinal analyses. Teachers and aides rated SCT, ADHD-IN, ADHD-hyperactivity/impulsivity (HI), opposi- tional defiant disorder (ODD), and depression along with academic impairment in 758 Spanish children (55 % boys) on three occasions (twice at the end of the first grade year [6- week separation] and then again 12-months later at the end of the second grade year). Three of eight SCT symptoms showed substantial loadings on the SCT factor and substantially higher loadings on the SCT factor than the ADHD-IN factor for teachers and aides at each assessment (seems drowsy , thinking is slow , and slow moving). Cross-sectional and lon- gitudinal analyses yielded similar results with SCT and ADHD-IN factors having different and unique external corre- lates (higher scores on SCT predicted lower scores on ADHD- HI and ODD while higher scores on ADHD-IN predicted higher scores on ADHD-HI and ODD with SCT and ADHD-IN both uniquely predicting academic impairment and depression). Developmental and methodological reasons are discussed for the failure to find an inconsistent alertness SCT factor (daydreams, alertness fluctuates, absent-minded, loses train of though, and confused). Keywords Sluggish cognitive tempo . ADHD . Psychometrics . Cross-cultural . Construct validity Sluggish cognitive tempo (SCT) is characterized by inconsis- tent alertness (alertness fluctuates, daydreaming, loses train of thought, and confusion) along with slow thinking/slow be- havior (thinking is slow, seems drowsy, and slow moving) (Lee et al. 2014). One research approach has sought to deter- mine if SCT symptoms could improve the validity of ADHD subtypes (e.g., division of ADHD-predominantly inattentive subtype in terms of high and low levels of SCT). Although some studies yielded positive results (Carlson and Mann 2002), most failed to show that SCT could significantly im- prove subtype validity (Marshall et al. 2014; Willcutt et al. 2014, Fig. 1). This failure encouraged the development of a second approach to SCT—that is, the study of SCT in its own right (see Barkley 2012, 2013 for reasons to study SCT in community and general clinical samples rather than only in individuals with a diagnosis of ADHD). This second approach has sought to determine if SCT and ADHD-inattention (IN) represent distinct factors with different external correlates (Barkley 2012, 2013; Becker et al. 2014b; Burns et al. 2013a; Jacobson et al. 2012; Lee et al. 2014; McBurnett et al. 2014; Penny et al. 2009; Willcutt et al. 2012, 2014). Although there is still debate on the best symptoms to represent SCT (Barkley 2014), factor analytic studies indicate that SCT is a different factor from ADHD-IN. These studies also suggest that SCT and ADHD-IN have unique and different external correlates although inconsistencies do occur here (e.g., some studies find SCT still predicts academic impairment after controlling for ADHD-IN while other studies do not find this unique association, Bauermeister et al. 2012; Becker et al. 2014a; Burns et al. 2013a; Langberg et al. 2014; Lee et al. 2014; McBurnett et al. 2014; Watabe et al. 2014). Variability in the external correlates of SCT is perhaps due to the use of M. Bernad : M. Servera : G. Grases University of the Balearic Islands & Research Institute on Health Sciences (IUNICS), Palma de Mallorca, Spain S. Collado University Rey Juan Carlos, Madrid, Spain G. L. Burns (*) Department of Psychology, Washington State University, Pullman, WA 99164-4820, USA e-mail: glburns@wsu.edu J Abnorm Child Psychol DOI 10.1007/s10802-014-9866-9