Objective: Eveningness diurnal preference is common in psychiatric conditions, including attention-deficit/hyperactivity disorder (ADHD) and internalizing disorders. Little is known about how diurnal preference relates to sluggish cognitive tempo (SCT)-a distinct clinical construct associated with functional impairment-in clinical samples.
Method: Adult outpatients (n = 65; 43 with ADHD, 22 with internalizing/adjustment disorders) self-reported on SCT symptoms (total symptoms; slow/daydreamy, sleepy/sluggish, and low initiation/persistence factors) and diurnal preference.
Results: Greater eveningness was associated with overall SCT severity and sleepy/sluggish symptoms in the full sample. Relationships between eveningness and overall SCT severity and slow/daydreamy symptoms were stronger for those with internalizing/adjustment disorders compared to ADHD. The relationship between eveningness and sleepy/sluggish symptoms was uniform across groups.
Conclusion: Findings suggest a potential role of eveningness preference in adult SCT presentation. Future studies should investigate underlying mechanisms linking these two constructs and the efficacy of circadian interventions in the treatment of SCT among adult outpatients.
Keywords: adult ADHD; chronotype; internalizing; sluggish cognitive tempo.