ebook_ADHD2019

114 Rohde, Buitelaar, Gerlach & Faraone Regarding group differences between individuals with ADHD and typically de- veloping subjects, a group of investigators led by colleagues in the Netherlands recently published a mega-analysis comparing more than 1700 brain scans of sub- jects with ADHD with around 1500 brain scans of individuals without ADHD. They found that several brain areas were different as a group in subjects with ADHD. Specifically, the volumes of the several parts of the brain such as the ac- cumbens, amygdala, caudate, hippocampus, putamen, and the total brain volume were smaller in individuals with ADHD compared with controls. 6 Finally, it is always important to remember that if the lack of a single brain abnormality in all ADHD brains is a valid argument to exclude ADHD from “the hall of medical disorders”, we must exclude all other mental disorders too! There is no unitary brain abnormality in all patients with autism, schizophrenia, depres- sion, bipolar disorder, dementia or anxiety disorders. HOW CAN A CHILD WHO SPENDS HOURS FOCUSED IN A VIDEOGAME HAVE ADHD? ISN’T ADHD JUST A NEW NAME FOR LAZINESS OR LACK OF WILLPOWER? The ability to focus attention and inhibit an action is strongly modulated by moti- vation. Thus, almost everybody, including the great majority of those affected by ADHD, can pay attention even for long periods of time when motivated. Our cur- rent understanding of brain mechanisms indicates that areas of our brain related to attention and the ability to orchestrate the execution of functions are flooded by an excitatory substance called dopamine in situations associated with motiva- Figure 6.1 Statistical significant between group differences (A) and group differences with suffi- cient magnitude to inform biomarkers (B) . A Group 1 Group 2 B Group 1 Group 2