The Adult Concentration Inventory (ACI) is an adult self-report measure of sluggish cognitive tempo (SCT) developed following a meta-analysis identifying items distinguishing SCT from attention-deficit/hyperactivity disorder (ADHD) inattention. To date, only one study conducted in college students has examined the structural and external validity of the ACI. The current study evaluated the convergent and discriminative validity of the ACI in a community sample of adults, in addition to testing unique associations with internalizing symptoms, daily life executive functions, and sleep. Adults (N = 286; Mage = 44.45; 83.6% female) completed ratings of SCT, ADHD symptom dimensions, and external correlates. An a priori two-factor model with cross-loadings found 10 of the 16 SCT items to have high loadings on the SCT factor and low loadings on the ADHD inattention factor. SCT was uniquely associated with higher internalizing symptoms, time management and self-organization difficulties, poorer sleep quality, shorter sleep duration, lower sleep efficiency, and more daytime sleepiness. These findings replicate and extend support for the ACI in assessing SCT in adults.
Keywords: ADHD; anxiety; depression; executive functions; factor analysis; sleep; sluggish cognitive tempo.