Análisis de la validez de constructo y predictiva de la dimensión Sluggish Cognitive Tempo en la infancia

Abstract

The dimension Sluggish Cognitive Tempo (SCT) or Slow Cognitive Tempo refers to the behavior observed in some children, characterized by excessive motor sluggishness, slow thinking, apathy, lack of motivation, inconsistent alertness, daydreaming confusion and drowsiness. Although there are historical references to a distinction between an attentional dysfunction represented by over-activation and another by under-activation, SCT emerged from the fieldwork to define the Attention Deficit Hyperactivity Disorder (ADHD) diagnostic criteria in DSM-III-R. Lahey et al. (1987) noted that the factor analytic studies identified a factor related but distinct from the Inattention (ADHD-IN) and Hyperactivity/Impulsivity (ADHD-HI) factors that could refer to as a "pure attentional" problem. This possible unique attention problem was, however, not included in the DSM-IV. During the decade of the nineties, research continued on SCT but it was with the working groups of DSM-5 when the research on the SCT dimension was greatly improved: many authors were interested in the definition of a "pure inattentive disorder”, even if SCT was not accepted in the DSM-5 either. One of the major problems related to SCT was the lack of a measure, specifically designed for its evaluation. Prior to the research of Penny et al. (2009), earlier research on SCT was forced to select items from other scales to represent this construct (e.g., the selection of three, four or five items from the CBCL that researchers viewed as representative of the SCT construct). As a result, SCT was represented by different sets of items as well as a small number of them. With traditional psychometric procedures, Penny and colleagues selected 14 items to define the SCT construct. These 14 items provided the basis for the development of measures of SCT (Barkley, 2012a, 2013; Becker, Luebbe, & Joyce, 2015; Lee et al., 2014; McBurnett et al., 2014). All of these new measures of SCT face the same basic problem, that is the empirical demonstration of convergent and discriminant validity of the SCT items. This is a necessary first step before research can meaningfully investigate if SCT and Inattention have unique and different external correlates. This thesis has three main objectives: (1) analyze the construct validity of the SCT dimension against the Inattention and ADHD in general; (2) compare the cross-sectional predictive validity of SCT and ADHD-Inattention dimensions; and (3) compare the longitudinal predictive validity of SCT and ADHD-Inattention dimensions. A more general goal of the research was the development and validation of a Spanish SCT scale for parent and teacher. The experimental design of this thesis combined cross-sectional and longitudinal data from a large sample of children evaluated four times in three years: twice the first year, when they were about 7 years of age (N = 758), once the second year (N = 718) and again the third year (N = 585). The main assessment instrument was the Child and Adolescent Disruptive Behavior Inventory (CADBI). This parent and teacher rating scale measures SCT, ADHD-IN, ADHD-HI, anxiety, depression, and oppositional defiant disorder along with academic and social impairment. The scores of the English version of the scale have demonstrated good reliability and validity (Lee et al., 2014). Other measures of social dysfunction and peer rejection in the classroom were also included in some of the studies in this research. All the studies included two raters in the home (i.e., mothers and fathers) along with two raters in the classroom (i.e., primary teachers and other teachers). Most of the analysis involved confirmatory factor analytic procedures along with structural regression procedures (based on structural ecuation models and latent traits) along with more traditional correlation analysis and reliability measurements. The first set of analysis evaluated the convergent and discriminant validity of the eight SCT items and the nine ADHD-IN items with ratings by mothers, fathers, primary teachers and other teachers. Five of the eight SCT items showed strong convergent and discriminant validity for ratings by mothers and fathers, with three of the eight SCT items showing strong convergent and discriminant validity for ratings by primary teachers and other teachers. All nine of the ADHD-IN symptoms showed convergent and discriminant validity. These analyses thus identified a set of SCT symptoms with convergent and discriminant validity for parents and teachers. The second set of analysis used a cross-sectional design to determine if SCT and ADHD-IN have unique external correlates (concurrent predictive validity). The results show that higher levels of SCT predicted significantly higher levels of internalizing behavior (anxiety and depression measures) along with higher levels of academic and social impairment, even after controlling for ADHD-IN. In addition, higher levels of SCT predicted lower levels of ADHD-HI and oppositional defiant disorder symptoms after controlling for ADHD-IN. On the other hand, higher levels of ADHD-IN predicted higher levels externalized symptoms, and also predicted more problems on most measures even after controlling for SCT. The third set of analysis used a longitudinal design to determine if SCT and ADHD-IN have unique external correlates across time. From the first to the second year, higher levels of SCT still predicted higher levels of depression along with higher levels of academic and social impairment problems and lower levels of ADHD-HI and oppositional deviant disorder symptoms even after controlling for ADHD-IN. From the first and second years to the third year, the outcomes were more complex. In the case of mothers and fathers, SCT continued to predict more problems such as depression symptoms, academic and social impairment even after controlling for ADHD-IN. However, for primary and other teachers, the unique correlates of SCT from the first and second year to the third year varied more: higher levels of SCT continued to predict higher levels of academic impairment and depression (with some exceptions), and lower levels of ADHD-HI even after controlling for ADHD-IN. Higher levels of SCT also continued predict lower levels of ADHD-HI across the time intervals after controlling for ADHD-IN. ADHD-IN remained a strong predictor of problematic outcomes across the one and two-year intervals even after controlling for SCT. The current research demonstrated that it was possible to identify SCT symptoms with convergent validity as well as discriminant validity relative to ADHD-IN symptom dimension. Also, the cross-sectional studies demonstrated that SCT has unique and different external correlates relative to ADHD-IN. After controlling for the overlap of SCT and ADHD-IN dimensions, both dimensions were able to uniquely predict more internalizing behavior problems (primarily depression) and more academic and social behavior problems. In contrast, while higher levels of ADHD-IN uniquely predicted higher levels of ADHD-HI and oppositional deviant disorder, SCT could be considered as a “protective factor” for these problems. The results from the longitudinal studies, although somewhat less consistent (especially in the case of teachers), confirmed this same trend. Although the findings from these studies indicate that SCT is a symptom dimension with internal and external validity relative to ADHD-IN dimension, it is still unclear if SCT should be viewed as a new attention disorder, like important authors as R. Barkley mentioned. We believe it is more prudent to consider SCT a “transdiagnòstic construct” (Becker et al., 2016). This means a dimension or trait common to the normal population (a continuum measure) where extreme scores may be a precursor or an aggravation of certain behavior disorders. From this point of view future research on SCT seems to fit perfectly under the “Research Domain Criteria”, a project to define reliable and valid psychopathological “domains” that may become an alternative to the categorical classification systems behavioral disorders that today represent the DSM-5 and ICD-10.