Symptom properties as a function of ADHD type: an argument for continued study of sluggish cognitive tempo.

Inconsistent alertness and orientation (sluggishness, drowsiness, daydreaming) were reported to accompany Attention Deficit Disorder (ADD) without Hyperactivity in DSM-III. Such Sluggish Cognitive Tempo items were tested in the DSM-IV Field Trial for ADHD, but were discarded from the Inattention symptom list because of poor negative predictive power. Using 692 children referred to a pediatric subspecialty clinic for ADHD, Sluggish Tempo items were re-evaluated. When Hyperactivity-Impulsivity was absent (i.e., using only cases of Inattentive Type plus clinic controls), Sluggish Tempo items showed substantially improved utility as symptoms of Inattention. Factor analyses distinguished a Sluggish Tempo factor from an Inattention factor. When DSM-IV ADHD types were compared, Inattentive Type was uniquely elevated on Sluggish Tempo. These findings suggest that (a) Sluggish Tempo items are adequate symptoms for Inattentive Type, or (b) Sluggish Tempo may distinguish two subtypes of Inattentive Type. Either conclusion is incompatible with ADHD nosology in DSM-IV.