Background-For candidate endophenotypes to be useful for psychiatric genetic research, they first of all need to show significant genetic influences. To address the relative lack of previous data, we set to investigate the extent of genetic and environmental influences on performance in a set of theoretically driven cognitive-experimental tasks in a large twin sample. We further aimed to illustrate how test-retest reliability of the measures affects the estimates.
Background-Attention-deficit hyperactivity disorder (ADHD) is one of the most common and highly heritable child psychiatric disorders. There is strong evidence that children with ADHD show slower and more variable responses in tasks such as Go/Nogo tapping aspects of executive functions like sustained attention and response control which may be modulated by motivational factors and/or state-regulation processes. The aim of this study was (1) to determine if these executive functions may constitute an endophenotype for ADHD; (2) to investigate for the first time whether known modulators of these executive functions may also be familial and (3) to explore whether gender has an impact on these measures.
BackgroundAdvances in both genetic and cognitive-experimental studies on attention deficit hyperactivity disorder (ADHD) have opened new opportunities for cognitive endophenotype research. In such genetic designs the focus is on individual differences in characteristics, associated with ADHD, that can be measured reliably over time. Genetic studies that take a 'quantitative trait loci' approach hypothesise that multiple susceptibility genes contribute to a continuous dimension of ADHD symptoms. As an important initial step, we aimed to investigate the underlying assumptions that (1) key cognitive-experimental tasks indicate adequate test-retest reliability and (2) ADHD symptom scores in a general population sample are associated with performance on these tasks.MethodsForty-nine children were assessed on a go/no-go task and a reaction time task (the 'fast task') that included manipulations with event rate and incentives. The children were assessed twice, with a test-retest interval of two weeks.ResultsThe majority of the task variables demonstrated moderate-to-good test-retest reliability. The correlations between teacher ratings of ADHD symptoms and key task variables were .4–.6: ADHD symptoms were associated with poor performance (especially high reaction time variability) in a slow baseline condition, whereas there was low or no association in conditions with a faster event rate or incentives. In contrast, no clear pattern of findings emerged based on parent ratings of ADHD symptoms.ConclusionThe data support the usefulness of the go/no-go and fast tasks for genetic studies, which require reliable and valid indices of individual differences. The overall pattern of associations between teacher ratings of ADHD symptoms and task variables is consistent with effects of event rate and incentives on performance, as predicted by the model of activation and arousal regulation. The lack of a clear pattern of findings with parent ratings of ADHD symptoms warrants further study.
Antenatal maternal anxiety has been shown to be related to infant temperament, childhood disorders, and impulsivity in adolescence. This study prospectively investigated whether antenatal maternal anxiety is associated with performance on a continuous performance task. Sixty-four adolescents (mean age, 15 y; 34 boys, 30 girls) were examined with a computerized continuous performance task (CPT) measuring sustained attention. Results showed that the CPT performance of boys of mothers with high levels of state anxiety during the 12th to 22nd postmenstrual week of pregnancy declined as the task progressed: their processing speed became slower and the variability in their reaction times increased. The study controlled for the possible confounding influences of postnatal maternal anxiety, the parents' educational level, and intelligence. Establishing a link between antenatal maternal anxiety and an objective measure of sustained attention/self-regulation, our results extend the growing evidence for an association between antenatal maternal anxiety and the neurobehavioral development of the offspring up into adolescence. A growing number of studies provide evidence that child development is negatively related to heightened maternal anxiety and stress during pregnancy (1-3). Prospective longitudinal studies, using behavioral questionnaires and clinical scales administered at several moments during development up to 9 y of age, revealed that children of mothers with high anxiety during pregnancy had more difficulties with cognitive, behavioral, and emotional self-regulation as expressed in infant difficult temperament, attention regulation problems, hyperactivity, clinical diagnosis of ADHD, ADHD symptoms, conduct disorders, and emotional problems (4 -9). One explanation for these observations, which is based on experimental studies in rodents and other animals, is that, during sensitive periods of development, disturbing factors (hormones related to maternal anxiety and/or stress) exercise organizational effects that constrain the malleability of biologic systems that ultimately can predispose to disorder (10,11).At present, it is not clear during which prenatal period the human fetus is most sensitive to the negative influence of the mother's emotional state. O'Connor et al. (7,8) found anxiety at 32 wk of pregnancy to be related to behavioral and emotional problems of both boys and girls, whereas anxiety at 18 wk of pregnancy was only in girls associated with these problems. In the second wave of their longitudinal study, Van den Bergh and Marcoen (9) pinpointed 12-22 wk as the only important period predictive of ADHD symptoms and externalizing and internalizing problems. In the first part of the third wave of this study, maternal anxiety during this period was found to be related to impulsivity during performance on a divided attention task and to lower scores on two intelligence subtests (12).This article represents a second part of the third wave of the prospective study of Van den Bergh and Marcoen (9) ...
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