Attention-deficit/hyperactivity disorder (ADHD)
Attention-deficit/hyperactivity disorder (ADHD), a state of serious impairments in both learning ability and social functioning, is one of many labels for one of the most prevalent conditions in child psychiatry, and, undoubtedly, the most controversial, which partly persists into adulthood. ADHD is conservatively estimated to occur in 3,0–7,5% of school-age children (Goldman et al., 1998), but more permissive criteria yield estimates of up to 17% (Barbaresi et al., 2002). Up to 20% of boys in some school systems receive psychostimulants for the treatment of ADHD (LeFever et al., 1999). Partly in response to legitimate concern about an apparent rapid increase in its prevalence in the 1990s, investigators have unsuccessfully attempted to formulate a single theory of ADHD, that would facilitate the development of an objective diagnosis test.
Aetiological factors of ADHD include not only genetic variations or mutations, but also environmental factors (brain injury and stroke, severe early deprivation, family psychosocial adversity and maternal smoking during pregnancy) and, most importantly and most difficult to identify, interactions between genes, and between genes and the environment. These factors are the initial causes of the multiple conditions that manifest symptomatically as ADHD, and their eventual identification should be accorded high priority.
The current criteria for the diagnosis of ADHD, published by the American Psychiatric Association in the 1994 Diagnostic and Statistical Manual of Mental Disorders (fourth edition; DSM-IV), are the most widely used and form our starting point. Other proposed criteria include those for the International Statistical Classification of Diseases and Related Health Problems (tenth revision; ICD-10) diagnosis of hyperkinetic disorder, which represents a more severe and ‘refined’ subset of DSM-IV ADHD, but which does not recognize the DSM-IV predominantly inattentive subtype (Castellanos & Tannock, 2002).Terms applied to ADHD include:
Three such endophenotypes
iii) deficits in working memory
are most amenable to integrative collaborative approaches that aim to uncover the causes of ADHD.
Working memory (WM) capacity is the ability to retain and manipulate information during a short period of time. This ability underlies complex reasoning and has generally been regarded as a fixed trait of the individual. Children with attention deficit hyperactivity disorder (ADHD) represent one group of subjects with a WM deficit, attributed to an impairment of the frontal lobe.
A previous preliminary study indicated that training of WM tasks can enhance executive functioning including working memory, response inhibition, and reasoning in children with ADHD (Klingberg et al., 2002b).
A randomized, controlled, double-blind trial to investigate the effect of improving working memory by computerized, systematic practice of WM tasks including 53 children with ADHD revealed a significant treatment effect both at intervention and follow-up (Klingberg et al., 2005).
The method evaluated in this study differs from that of previous ones in that it focuses entirely on training WM tasks. Moreover, the training is computerized, which makes it possible to automatically and continuously adapt the difficulty level to the performance of the child to optimize the training effect. Executive functions were measured and ADHD symptoms were rated before, immediately after, and 3 months after intervention.
A significant effect was shown for the span-board task, a visuospatial working memory task, that was not part of the training program, as well as for tasks measuring verbal WM, response inhibition, and complex reasoning. Moreover, parent ratings demonstrated significant reduction in symptoms of inattention and hyperactivity/impulsivity.
Working memory can be improved by training in children with ADHD and could be of clinical use for ameliorating the symptoms in ADHD. Altogether, the effect sizes for reduction of inattention are clinically strong.
•Deficits in executive functioning, including working memory deficits, have been suggested to play an important role in attention-deficit/hyperactivity disorder (ADHD).
•A current study showed that working memory can be improved by training. In addition, there were effects on reasoning, response inhibition, and a decrease in parent-rated symptoms of ADHD.
•The subjects that would be expected to benefit from training of working memory are presumably those individuals for whom executive deficits and inattention problems constitute a bottleneck for everyday functioning or academic performance.
•It is also possible that training of working memory will be useful in other conditions in which working memory deficits are prominent, such as after traumatic brain injury and stroke affecting the frontal lobe.
Goldman LS, Genel M, Bezman RJ, Slanetz PJ. Diagnosis and treatment of attention-deficit/hyperactivity disorder in children and adolescents. Council on Scientific Affairs, American Medical Association. JAMA 1998;279(14):1100-7
LeFever GB, Dawson KV, Morrow AL. The extent of drug therapy for attention deficit-hyperactivity disorder among children in public schools. Am J Public Health 1999;89(9):1359-64
Barbaresi WJ, Katusic SK, Colligan RC, et al. How common is attention-deficit/hyperactivity disorder? Incidence in a population-based birth cohort in Rochester, Minn. Arch Pediatr Adolesc Med 2002;156(3):217-24
Castellanos FX, Tannock R. Neuroscience of attention-deficit/hyperactivity disorder: the search for endophenotypes. Nat Rev Neurosci 2002;3(8):617-28
Klingberg T, Fernell E, Olesen PJ, et al. Computerized training of working memory in children with ADHD--a randomized, controlled trial. J Am Acad Child Adolesc Psychiatry 2005;44(2):177-86
Klingberg T, Forssberg H, Westerberg H. Training of working memory in children with ADHD. J Clin Exp Neuropsychol 2002;24(6):781-91
Maria Vrijmoed-de Vries | alfa
One gene closer to regenerative therapy for muscular disorders
01.06.2017 | Cincinnati Children's Hospital Medical Center
The gut microbiota plays a key role in treatment with classic diabetes medication
01.06.2017 | University of Gothenburg
An international team of scientists has proposed a new multi-disciplinary approach in which an array of new technologies will allow us to map biodiversity and the risks that wildlife is facing at the scale of whole landscapes. The findings are published in Nature Ecology and Evolution. This international research is led by the Kunming Institute of Zoology from China, University of East Anglia, University of Leicester and the Leibniz Institute for Zoo and Wildlife Research.
Using a combination of satellite and ground data, the team proposes that it is now possible to map biodiversity with an accuracy that has not been previously...
Heatwaves in the Arctic, longer periods of vegetation in Europe, severe floods in West Africa – starting in 2021, scientists want to explore the emissions of the greenhouse gas methane with the German-French satellite MERLIN. This is made possible by a new robust laser system of the Fraunhofer Institute for Laser Technology ILT in Aachen, which achieves unprecedented measurement accuracy.
Methane is primarily the result of the decomposition of organic matter. The gas has a 25 times greater warming potential than carbon dioxide, but is not as...
Hydrogen is regarded as the energy source of the future: It is produced with solar power and can be used to generate heat and electricity in fuel cells. Empa researchers have now succeeded in decoding the movement of hydrogen ions in crystals – a key step towards more efficient energy conversion in the hydrogen industry of tomorrow.
As charge carriers, electrons and ions play the leading role in electrochemical energy storage devices and converters such as batteries and fuel cells. Proton...
Scientists from the Excellence Cluster Universe at the Ludwig-Maximilians-Universität Munich have establised "Cosmowebportal", a unique data centre for cosmological simulations located at the Leibniz Supercomputing Centre (LRZ) of the Bavarian Academy of Sciences. The complete results of a series of large hydrodynamical cosmological simulations are available, with data volumes typically exceeding several hundred terabytes. Scientists worldwide can interactively explore these complex simulations via a web interface and directly access the results.
With current telescopes, scientists can observe our Universe’s galaxies and galaxy clusters and their distribution along an invisible cosmic web. From the...
Temperature measurements possible even on the smallest scale / Molecular ruby for use in material sciences, biology, and medicine
Chemists at Johannes Gutenberg University Mainz (JGU) in cooperation with researchers of the German Federal Institute for Materials Research and Testing (BAM)...
19.06.2017 | Event News
13.06.2017 | Event News
13.06.2017 | Event News
23.06.2017 | Physics and Astronomy
23.06.2017 | Life Sciences
23.06.2017 | Information Technology