Sluggish cognitive tempo : a unique subtype of ADHD-PI or just a symptom?
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Attention Deficit Hyperactivity Disorder (ADHD) is one of the most commonly diagnosed of child clinical syndromes and is associated with poor academic achievement, poor peer and family relations, and an elevated risk for anxiety, depression, and conduct disorder (Barkley ,1990; Barkley, Guevremont, Anastopoulos, DuPaul, & Shelton, 1993; Barkley, Murphy, & Kwasnik, 1996; Beiderman, Faraone, & Lapey, 1992; Fischer, Fischer, et al., 1990; Hinshaw, 1994; Nadeau 1995; Weiss & Hechtman, 1993). Although ADHD is one of the most commonly diagnosed and widely researched disorders, the diagnostic criteria and defining characteristics of ADHD remain controversial (Wolraich, 1999). The current diagnostic formulation, as specified by the DSM-IV-TR, includes three distinct subtypes: Attention Deficit Hyperactivity Disorder- Predominantly Hyperactive Impulsive Type (ADHD-H), Attention Deficit Hyperactivity Predominantly Inattentive Type (ADHD-PI) and Attention Deficit Hyperactivity Disorder- Combined Typed (ADHD-C). Perhaps the most controversial aspect of the current nosology is the inclusion of the inattention symptoms within the family of ADHD diagnoses (Milich, Balentine, Lynam, 2001). Researchers and clinicians have further posited that ADHD-PI represents a distinct disorder with two subtypes: inattentive-disorganized and sluggish cognitive tempo. This study explored the relation between reading fluency, sluggish cognitive tempo symptoms, disorganized symptoms, processing speed and ADHD diagnosis. This study examined performance of children diagnosed 77 children diagnosed with ADHD (i.e. 53 participants met criteria for ADHD-PI and 24 participants met criteria for ADHD-C) on measures of cognitive functioning, processing speed, behavioral reports, sluggish cognitive tempo, disorganization and reading fluency. Significant group differences did not emerge on measures of processing speed, sluggish cognitive tempo symptoms or disorganized symptoms. Path analysis was employed to examine the simultaneous effects of processing speed on inattention symptoms, hyperactive/impulsive symptoms, SCT symptoms, DO symptoms, reading fluency, and internalizing symptoms. In addition, the paths from SCT symptoms, DO symptoms, inattention symptoms, and hyperactive/impulsive symptoms to reading fluency and internalizing symptoms were also be examined. Processing speed had a significant direct effect on SCT symptoms, Inattention Symptoms and Reading Fluency. In addition, SCT symptoms had a significant direct effect on anxiety symptoms. In summary, findings from the study provide important information about the link between processing speed, attention written, and reading fluency. Limitations of the study and implications for future research and practice are discussed.