ADHD Research News
Reprinted with permission of Journal of Attention
Disorders
Bekker, E.M., Overtoom, C.C., Kenemans, J.L., Kooij,
J.J., DeNoord, J., Buitelaar, K., & Verbaten, M.N.
(2005). Stopping and changing in adults with ADHD.
Psychological Medicine, 35, 807-816.
Twenty-four adults with ADHD - Combined Type
completed a stop-signal task in which each subject
must withhold quick responding to a cue when
signaled by a tone. Additionally, a stop-change
version was also administered in which participants
had to provide an alternative motor response when
they heard the tone. Compared to twenty-four
controls, adults with ADHD took a significantly
longer time to inhibit and to change their response.
The authors hypothesized their results support a
core deficit of behavioral inhibition in adults with
ADHD.
Bellgrove, M.A., Hawi, Z., Karley, A., Gill, M., &
Robertson, I.H. (2005). Dissecting the ADHD
phenotype: Sustained attention, response variability
and spatial attention asymmetries in relation to
dopamine transporter (DAT1) genotype.
Neuropsychologia, 43, 1847-1857.
In a population of 22 children and adolescents with
ADHD, the presence of multiple copies of the DAT1
repeat allele was used to classify youth as either
high or low risk. The high risk (two copies) group
demonstrated higher scores on multiple behavioral
scales and a computerized assessment of attention.
The authors suggest that deficits in sustained
attention are more strongly associated with ADHD in
individuals who have two copies of the 10-repeat
DAT1 allele. The high risk ADHD group demonstrated
reduced left-side attentional asymmetry compared to
the low risk group only. The authors suggest
genotyping should be used in the future to determine
whether heterogeneity in neuropsychological profiles
for those with ADHD is related to genetic
heterogeneity. They propose that such studies might
define meaningful subgroups of youth with ADHD.
Biederman, J., Kwon, A., Aleardi, M., Chouinard, V.,
Marino, T., Cole, H., Mick, E., & Faraone, S.V.
(2005). Absence of gender effects on ADHD: Findings
in non-referred subjects. American Journal of
Psychiatry, 162, 1083-1089.
Clinic referred samples of youth with ADHD find that
boys demonstrate significantly greater degrees of
disruptive behavior and learning disability than
females. In this study of nearly 600 non-referred
siblings of ADHD probands, a structured diagnostic
interview and additional assessment instruments were
used. Approximately 11% of the female, non-referred
siblings met criteria for ADHD while approximately
30% of the males met criteria. When comparing the
boys with ADHD to girls, the prevalence of subtypes
among them was equal with the combined subtype
presenting in approximately 60%. The groups did not
differ with respect to psychiatric comorbidity of
internalizing or externalizing disorders. Levels
and types of impairment associated with symptoms
were also not different. Types and frequency of
treatment also did not differ by gender for those
meeting criteria with ADHD. The authors concluded
the associated features of ADHD do not differ by
gender and that previously detected differences are
likely the result of referral bias, especially
biases based on referral due to more severe
disruptive behavior disorders that present as
comorbid with ADHD.
