Sluggish Cognitive Tempo, Processing Speed, and Internalizing Symptoms: the Moderating Effect of Age.

Sluggish Cognitive Tempo (SCT) has been defined by a constellation of caregiver-reported symptoms that includes daydreaming, difficulty initiating and sustaining effort, lethargy, and physical underactivity. These symptoms have been observed in both typically developing children and in some children with Attention-Deficit/Hyperactivity Disorder (ADHD)-especially those with the predominantly inattentive presentation. Symptoms of SCT (typically identified via rating scales) appear separable from DSM inattentive ADHD symptoms, but have also been associated with internalizing symptoms. To date, however, few studies have examined associations among ratings of SCT and speeded performance-based measures. The present study examined associations among SCT, processing speed, and internalizing symptoms in a sample of 566 clinically referred children (65% male), while also considering how these associations change with age. Findings revealed small but significant age-related differences in the strength of associations between the "Daydreamy" element of SCT and processing speed (as measured by the WISC-IV Processing Speed Index-PSI), with stronger associations observed in younger children. Importantly, this difference in strength of association was not accounted for by the change in WISC-IV test forms for PSI subtests between 6-7 year-olds and 8-16 year-olds. Conversely, the association between SCT and internalizing symptoms remained generally consistent across the age range. Findings contribute to further characterization of the "slowness" of responding seen in SCT and may have implications for behavioral intervention.