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
Routing gene therapy directly into the brain
07.12.2017 | Boston Children's Hospital
New Hope for Cancer Therapies: Targeted Monitoring may help Improve Tumor Treatment
01.12.2017 | Berliner Institut für Gesundheitsforschung / Berlin Institute of Health (BIH)
MPQ scientists achieve long storage times for photonic quantum bits which break the lower bound for direct teleportation in a global quantum network.
Concerning the development of quantum memories for the realization of global quantum networks, scientists of the Quantum Dynamics Division led by Professor...
Researchers have developed a water cloaking concept based on electromagnetic forces that could eliminate an object's wake, greatly reducing its drag while...
Tiny pores at a cell's entryway act as miniature bouncers, letting in some electrically charged atoms--ions--but blocking others. Operating as exquisitely sensitive filters, these "ion channels" play a critical role in biological functions such as muscle contraction and the firing of brain cells.
To rapidly transport the right ions through the cell membrane, the tiny channels rely on a complex interplay between the ions and surrounding molecules,...
The miniaturization of the current technology of storage media is hindered by fundamental limits of quantum mechanics. A new approach consists in using so-called spin-crossover molecules as the smallest possible storage unit. Similar to normal hard drives, these special molecules can save information via their magnetic state. A research team from Kiel University has now managed to successfully place a new class of spin-crossover molecules onto a surface and to improve the molecule’s storage capacity. The storage density of conventional hard drives could therefore theoretically be increased by more than one hundred fold. The study has been published in the scientific journal Nano Letters.
Over the past few years, the building blocks of storage media have gotten ever smaller. But further miniaturization of the current technology is hindered by...
With innovative experiments, researchers at the Helmholtz-Zentrums Geesthacht and the Technical University Hamburg unravel why tiny metallic structures are extremely strong
Light-weight and simultaneously strong – porous metallic nanomaterials promise interesting applications as, for instance, for future aeroplanes with enhanced...
11.12.2017 | Event News
08.12.2017 | Event News
07.12.2017 | Event News
12.12.2017 | Physics and Astronomy
12.12.2017 | Earth Sciences
12.12.2017 | Power and Electrical Engineering