ebook_ADHD2019_engl.

ADHD is a common neurodevelopmental disorder that typically has onset in childhood, most often between age 6 and 12. Despite thousands of research papers on ADHD are being published each year, our understanding of the neurobiology of ADHD is still limited. It is clear, however, that ADHD is characterized by substantial heterogeneity across many, if not all, levels of analysis. This chapter will review this heterogeneity with respect to the neurobiological mechanisms that underping ADHD, starting with biochemistry and metabolomics, and then continuing with cog- nition, up to functional and structural alterations of the brain. NEUROCHEMISTRYAND METABOLOMICS Knowledge about the neurochemistry of ADHD has thus far largely relied on serendipity and coincidental findings, e.g. from medication studies and work in animal models. Additional evidence for the involvement of those basic pathways comes from genetics as well as first metabolite biomarker studies. For example, a comprehensive meta-analysis of potential biomarkers found several measures, specifically norepinephrine (NE), monoamine oxidase (MAO), 3-methoxy-4-hy- droxyphenylethylene glycol (MHPG), zink, ferritin, and cortisol, to be significantly UNDERSTANDING THE ESSENTIALS OF THE ADHD NEUROBIOLOGY Jan K. Buitelaar Dennis van der Meer Jennifer Richards 2