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Fuermaier A.B.M.,University of Groningen | Tucha L.,University of Groningen | Evans B.L.,University of Groningen | Koerts J.,University of Groningen | And 6 more authors.
Journal of Neural Transmission | Year: 2015

Adults with attention deficit hyperactivity disorder (ADHD) suffer from various impairments of cognitive, emotional and social functioning, which can have considerable consequences for many areas of daily living. One of those areas is driving a vehicle. Driving is an important activity of everyday life and requires an efficient interplay between multiple cognitive, perceptual, and motor skills. In the present study, a selective review of the literature on driving-related difficulties associated with ADHD is performed, seeking to answer whether individuals with ADHD show increased levels of unsafe driving behaviours, which cognitive (dys)functions of individuals with ADHD are related to driving difficulty, and whether pharmacological treatment significantly improves the driving behaviour of individuals with ADHD. The available research provides convincing evidence that individuals with ADHD have different and more adverse driving outcomes than individuals without the condition. However, it appears that not all individuals with ADHD are affected uniformly. Despite various cognitive functions being related with driving difficulties, these functions do not appear helpful in detecting high risk drivers with ADHD, nor in predicting driving outcomes in individuals with ADHD, since impairments in these functions are defining criteria for the diagnoses of ADHD (e.g., inattention and impulsivity). Pharmacological treatment of ADHD, in particular stimulant drug treatment, appears to be beneficial to the driving difficulties experienced by individuals with ADHD. However, additional research is needed, in particular further studies that address the numerous methodological weaknesses of many of the previous studies. © 2015 The Author(s) Source

Toulopoulou T.,University of Hong Kong | Toulopoulou T.,Kings College London | Van Haren N.,University Utrecht | Zhang X.,University of Hong Kong | And 18 more authors.
Molecular Psychiatry | Year: 2015

In aetiologically complex illnesses such as schizophrenia, there is no direct link between genotype and phenotype. Intermediate phenotypes could help clarify the underlying biology and assist in the hunt for genetic vulnerability variants. We have previously shown that cognition shares substantial genetic variance with schizophrenia; however, it is unknown if this reflects pleiotropic effects, direct causality or some shared third factor that links both, for example, brain volume (BV) changes. We quantified the degree of net genetic overlap and tested the direction of causation between schizophrenia liability, brain structure and cognition in a pan-European schizophrenia twin cohort consisting of 1243 members from 626 pairs. Cognitive deficits lie upstream of the liability for schizophrenia with about a quarter of the variance in liability to schizophrenia explained by variation in cognitive function. BV changes lay downstream of schizophrenia liability, with 4% of BV variation explained directly by variation in liability. However, our power to determine the nature of the relationship between BV deviation and schizophrenia liability was more limited. Thus, while there was strong evidence that cognitive impairment is causal to schizophrenia liability, we are not in a position to make a similar statement about the relationship between liability and BV. This is the first study to demonstrate that schizophrenia liability is expressed partially through cognitive deficits. One prediction of the finding that BV changes lie downstream of the disease liability is that the risk loci that influence schizophrenia liability will thereafter influence BV and to a lesser extent. By way of contrast, cognitive function lies upstream of schizophrenia, thus the relevant loci will actually have a larger effect size on cognitive function than on schizophrenia. These are testable predictions. © 2015 Macmillan Publishers Limited Molecular Psychiatry. Source

Fuermaier A.B.M.,University of Groningen | Tucha L.,University of Groningen | Koerts J.,University of Groningen | Aschenbrenner S.,SRH Clinic Karlsbad Langensteinbach | And 4 more authors.
Clinical Neuropsychologist | Year: 2014

Executive dysfunction of adults with ADHD is often associated with poor self-awareness of problems, such as in emotional competence, emotional recognition, and driving competence. However, with regard to cognitive functioning, little is known about how adults with ADHD evaluate their own cognitive performance. A total of 77 adults with ADHD and 116 healthy adults were assessed with self-report scales measuring several aspects of cognition. Significance and effect sizes as well as the proportion of patients perceiving impairments were calculated. Further analysis was carried out on the frequency of patients perceiving various types of impairments. Adults with ADHD perceived themselves to have significant and severe dysfunction in all areas of cognition assessed as a group. Furthermore, the majority of patients reported multiple impairments in attention, memory and executive functioning. The present study demonstrated that adults with ADHD are aware of problems in cognitive functioning as shown by considerable perceived neuropsychological impairment in the majority of patients. Patients with ADHD tended to report cognitive impairments in multiple domains rather than impairments in specific functions. © 2014 Taylor & Francis. Source

Tucha L.,University of Groningen | Fuermaier A.B.M.,University of Groningen | Koerts J.,University of Groningen | Buggenthin R.,University of Groningen | And 6 more authors.
Journal of Neural Transmission | Year: 2015

Neuropsychological research on adults with ADHD showed deficits in various aspects of attention. However, the majority of studies failed to explore the change of performance over time, so-called time-on-task effects. As a consequence, little is known about sustained attention performance of adults with ADHD. The aim of the present study was therefore to test the hypothesis of sustained attention deficits of adults with ADHD. Twenty-nine adults with ADHD and 30 healthy individuals were assessed on four 20-min tests of sustained attention, measuring alertness, selective attention, divided attention and flexibility. The deterioration of performance over time (time-on-task effects) was compared between patients with ADHD and healthy individuals to conclude on sustained attention performance. Compared to healthy individuals, patients with ADHD showed significant deficits of medium size in selective attention and divided attention. Furthermore, medium sustained attention deficits was observed in measures of alertness, selective attention and divided attention. This study supports the notion of sustained attention deficits of adults with ADHD. © 2015 The Author(s) Source

Fuermaier A.B.M.,University of Groningen | Tucha L.,University of Groningen | Koerts J.,University of Groningen | Aschenbrenner S.,SRH Clinic Karlsbad Langensteinbach | And 4 more authors.
PLoS ONE | Year: 2013

Objectives: The context of memory experiences is referred to as source memory and can be distinguished from the content of episodic item memory. Source memory represents a crucial part of biographic events and elaborate memory experiences. Whereas individuals with attention deficit hyperactivity disorder (ADHD) were shown to have inefficient item memory, little is known about the context of memory experiences. Methods: The present study compared 37 adult patients with a diagnosed ADHD with 40 matched healthy participants on a word list paradigm. Memory functions of encoding, retention and source discrimination were assessed. Furthermore, standardized measures of memory and executive control were applied in order to explore a qualitative differentiation of memory components. Results: Adult patients with ADHD showed impaired performance in encoding of new information whereas the retention of encoded items was found to be preserved. The most pronounced impairment of patients with ADHD was observed in source discrimination. Regression models of cognitive functions on memory components supported some qualitative differentiation. Conclusions: Data analysis suggests a differential pattern of memory impairment in adults suffering from ADHD with a particular deficit in source discrimination. Inefficient source discrimination in adults with ADHD can affect daily functioning by limiting biographic awareness and disturbing general cognitive processes. © 2013 Fuermaier et al. Source

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