Are there cognitive subtypes in adult attention deficit/hyperactivity disorder?

There has been increasing knowledge of the treatment, diagnosis, and demogr aphics of adults with residual attention deficit/hyperactivity disorder (AD HD). However, less is known about the neuropsychological functioning in adu lts with residual ADHD. In comparing the clinical neuropsychological test p erformance of a group of adult clinic patients with residual ADHD (N = 30) with that of normal controls (N = 10), we found the patients performed wors e on the Trail Making Test, a visual continuous performance test, and the " Brown-Peterson" Auditory Consonant Trigrams Test, but not on any other neur opsychological measures. This pattern indicated a deficit in the area of ex ecutive control type functioning a functional deficit that could be linked to dysregulation of frontal lobe brain systems. Of equal interest was that patients diagnosed with ADHD/hyperactive impulsive type (ADHD+) and patient s diagnosed with ADHD/inattentive type (ADHD-) had different types of execu tive system deficits. ADHD+ was associated with relative deficiency on the Wisconsin Card Sorting Test. ADHD- was associated with relative deficiency on the "Brown-Peterson" Auditory Consonant Trigrams Test, a measure of work ing memory, as well as less olfactory identification on a smell identificat ion test The data are discussed in terms of recent localization theories of frontal lobe function. The preliminary data suggest that the different cog nitive weaknesses of ADD subtypes may be linked to dysregulation of separat e frontal brain regions and/or neurotransmitter systems.