ABSTRACT
BACKGROUND: Current classification systems do not allow for comorbid diagnoses of attention deficit hyperactivity disorder (ADHD) and autistic spectrum disorder (ASD). Children with ADHD are often screened for ASD during clinical assessment and when recruited to clinical trials. We predicted that children with ADHD would have more autistic traits than controls and that certain traits would be more prevalent. METHODS: The clinically referred sample consisted of 30 children with ADHD and 30 matched controls aged 9-15 years. Children were screened for ASD traits using the Social Aptitudes Scale (SAS) and the Social Communication Questionnaire (SCQ). RESULTS: We found that ASD traits were significantly higher in children with ADHD than controls. None of the children received a diagnosis of autism or ASD. However, a large proportion (28% using the SCQ and 62% using the SAS) of children with ADHD reached screening thresholds for a predictive diagnosis of ASD. Relative to controls, children with ADHD had significantly higher levels of communication and social deficits, but not repetitive behaviours. CONCLUSION: Further work is needed to establish whether autistic-like communication and social difficulties in children with ADHD are part of the broader ASD phenotype or are specific to ADHD.
Subject(s)
Attention Deficit Disorder with Hyperactivity/complications , Autistic Disorder/complications , Psychiatric Status Rating Scales , Adolescent , Age Factors , Case-Control Studies , Child , Child Behavior , Comorbidity , Female , Humans , Male , Models, TheoreticalABSTRACT
Tourette Syndrome (TS) is a developmental neurological condition that is characterised by the presence of multiple motor and one or more vocal tics. Tics are highly stereotyped repetitive behaviours that fluctuate in type, complexity and severity. TS has been linked to impaired cognitive control processes, however, a recent study (Mueller et al. in Curr Biol 16:570-573, 2006) demonstrated that young people with TS, although exhibiting chronic motor and vocal tics, nevertheless performed significantly better than a group of age-matched controls on a task that required extremely high levels of cognitive control (i.e., predictably shifting between executing pro-saccade and anti-saccade responses to a visual stimulus). As predictable task sequences allow task-related cognitive processes to commence prior to the presentation of target stimuli we examined whether the superior performance of the TS group could be replicated when task sequences were varied unpredictably. Our results confirmed that both the TS group and an age-matched control group benefited, by the same extent, when the saccade task (pro-saccade vs. anti-saccade) was pre-cued. In contrast, while the control group showed a significant decrease in performance on task switch trials relative to task repetition trials-the TS group exhibited no significant 'costs' of switching task. While task performance was modulated by response and target location shifts in the control group, these factors had less impact on the TS group's performance on task switch trials. These results confirm and extend the previous demonstration that individuals with TS exhibit paradoxically greater levels of cognitive control than healthy controls.
Subject(s)
Cognition/physiology , Motor Activity/physiology , Tourette Syndrome/physiopathology , Adolescent , Analysis of Variance , Case-Control Studies , Eye Movements/physiology , Female , Humans , Male , Neuropsychological Tests , Photic Stimulation/methods , Reaction Time/physiology , Task Performance and AnalysisABSTRACT
Association between attention-deficit hyperactivity disorder (ADHD) and the 10-repeat allele of the dopamine transporter gene (DAT1) has been reported in independent clinical samples using a categorical clinical definition of ADHD. The present study adopts a quantitative trait loci (QTL) approach to examine the association between DAT1 and a continuous measure of ADHD behaviours in a general-population sample, as well as to explore whether there is an independent association between DAT1 and performance on neuropsychological tests of attention, response inhibition, and working memory. From an epidemiological sample of 872 boys aged 6-11 years, we recruited 58 boys scoring above the 90th percentile for teacher reported ADHD symptoms (SWAN ADHD scale) and 68 boys scoring below 10th percentile for genotyping and neuropsychological testing. A significant association was found between the DAT1 homozygous 10/10-repeat genotype and high-scoring boys (chi(2)square=4.6, P<0.03; odds ratio=2.4, 95% CI 1.1-5.0). Using hierarchical linear regression, a significant independent association was found between the DAT1 10/10-repeat genotype and measures of selective attention and response inhibition after adjusting for age, IQ, and ADHD symptoms. There was no association between DAT1 and any component of working memory. Furthermore, performance on tasks of selective attention although associated with DAT1 was not associated with SWAN ADHD high scores after controlling for age and IQ. In contrast, impairment on tasks that tapped sustained attention and the central executive component of working memory were found in high-scoring boys after adjusting for age and IQ. The results suggest that DAT1 is a QTL for continuously distributed ADHD behaviours in the general population and the cognitive endophenotype of response inhibition.
