Fetal alcohol spectrum disorder (FASD) is a common neurodevelopmental condition associated with deficits in cognitive functioning (executive functioning [EF], attention, working memory, etc.), behavioral impairments, and abnormalities in brain structure including cortical and subcortical volumes. Rates of comorbid attention-deficit/hyperactivity disorder (ADHD) are high in children with FASD and contribute to significant functional impairments. Sluggish cognitive tempo (SCT) includes a cluster of symptoms (e.g. underactive/slow-moving, confusion, fogginess, daydreaming) found to be related to but distinct from ADHD, and previous research suggests that it may be common in FASD. We explored SCT by examining the relationship between SCT and both brain volumes (corpus callosum, caudate, and hippocampus) and objective EF measures in children with FASD vs. typically developing controls.

This is a secondary analysis of a larger longitudinal CIFASD study that consisted of 35 children with prenatal alcohol exposure (PAE) and 30 controls between the ages of 9 to 18 at follow-up. Children completed a set of cognitive assessments (WISC-IV, DKEFS, & NIH Toolbox) and an MRI scan, while parents completed the Child Behavior Checklist (CBCL), which includes a SCT scale. We examined group differences between PAE and controls in relation to SCT symptoms, EF scores, and subcortical volumes. Then, we performed within-and between-group comparisons with and without controlling for total intracranial volume, age, attention problems, and ADHD problems between SCT and subcortical brain volumes. Finally, we performed correlations between SCT and EF measures for both groups.

Compared to controls, participants with PAE showed significantly more SCT symptoms on the CBCL (t [57] = 3.66, p = 0.0006), more parent-rated attention problems and ADHD symptoms, lower scores across several EF measures (DKEFS Trail-Making and Verbal Fluency; WISC-IV Digit Span, Symbol Search, and Coding; effect sizes ranging from 0.44 to 1.16), and smaller regional volumes in the caudate, hippocampus, and posterior areas of the corpus callosum. In the PAE group, a smaller hippocampus was associated with more SCT symptoms (controlling for parent-rated attention problems and ADHD problems, age, and intracranial volume). However, in the control group, a larger mid posterior and posterior corpus callosum were significantly associated with more SCT symptoms (controlling for parent-rated attention problems, intracranial volume, and age; r [24] = 0.499, p = 0.009; r [24] = 0.517, p = 0.007). In terms of executive functioning, children in the PAE group with more SCT symptoms performed worse on letter sequencing of the Trail-Making subtest (controlling attention problems & ADHD symptoms). In comparison, those in the control group with more SCT symptoms performed better on letter sequencing and combined number letter sequencing of the Trail-Making subtest (controlling attention problems).

Findings suggest that children with FASD experience elevated SCT symptoms compared to typically developing controls, which may be associated with worse performance on EF tasks and smaller subcortical volumes (hippocampus) when taking attention difficulties and ADHD symptoms into account. Additional research into the underlying causes and correlates of SCT in FASD could result in improved tailoring of interventions for this population.