Editing Attention deficit hyperactivity disorder (section)

=== Brain structure ===
[[File:Attention deficit hyperactivity disorder - Attention deficit hyperactivity disorder - Reduced brain volume on the left side from ADHD.jpg|thumb|upright=1.3|The left prefrontal cortex, shown here in blue, is often affected in ADHD]]
In children with ADHD, there is a general reduction of volume in certain brain structures, with a proportionally greater decrease in the volume in the left-sided prefrontal cortex.<ref name="Malenka ADHD neurosci" /><ref name="Krain2006">{{cite journal |vauthors=Krain AL, Castellanos FX |title=Brain development and ADHD |journal=[[Clinical Psychology Review]] |volume=26 |issue=4 |pages=433–444 |date=August 2006 |pmid=16480802 |doi=10.1016/j.cpr.2006.01.005}}</ref> The [[posterior parietal cortex]] also shows thinning in individuals with ADHD compared to controls. Other brain structures in the prefrontal-striatal-cerebellar and prefrontal-striatal-thalamic circuits have also been found to differ between people with and without ADHD.<ref name="Malenka ADHD neurosci" /><ref name="pmid22169776" /><ref name="pmid22983386" />

The subcortical volumes of the [[accumbens]], [[amygdala]], [[Caudate nucleus|caudate]], [[hippocampus]], and [[putamen]] appears smaller in individuals with ADHD compared with controls.<ref>{{cite journal |vauthors=Hoogman M, Bralten J, Hibar DP, Mennes M, Zwiers MP, Schweren LS, van Hulzen KJ, Medland SE, Shumskaya E, Jahanshad N, Zeeuw P, Szekely E, Sudre G, Wolfers T, Onnink AM, Dammers JT, Mostert JC, Vives-Gilabert Y, Kohls G, Oberwelland E, Seitz J, Schulte-Rüther M, Ambrosino S, Doyle AE, Høvik MF, Dramsdahl M, Tamm L, van Erp TG, Dale A, Schork A, Conzelmann A, Zierhut K, Baur R, McCarthy H, Yoncheva YN, Cubillo A, Chantiluke K, Mehta MA, Paloyelis Y, Hohmann S, Baumeister S, Bramati I, Mattos P, Tovar-Moll F, Douglas P, Banaschewski T, Brandeis D, Kuntsi J, Asherson P, Rubia K, Kelly C, Martino AD, Milham MP, Castellanos FX, Frodl T, Zentis M, Lesch KP, Reif A, Pauli P, Jernigan TL, Haavik J, Plessen KJ, Lundervold AJ, Hugdahl K, Seidman LJ, Biederman J, Rommelse N, Heslenfeld DJ, Hartman CA, Hoekstra PJ, Oosterlaan J, Polier GV, Konrad K, Vilarroya O, Ramos-Quiroga JA, Soliva JC, Durston S, Buitelaar JK, Faraone SV, Shaw P, Thompson PM, Franke B |title=Subcortical brain volume differences in participants with attention deficit hyperactivity disorder in children and adults: a cross-sectional mega-analysis |journal=[[The Lancet Psychiatry]] |volume=4 |issue=4 |pages=310–319 |date=April 2017 |pmid=28219628 |pmc=5933934 |doi=10.1016/S2215-0366(17)30049-4}}</ref> Structural MRI studies have also revealed differences in white matter, with marked differences in inter-hemispheric asymmetry between ADHD and typically developing youths.<ref>{{cite journal |vauthors=Douglas PK, Gutman B, Anderson A, Larios C, Lawrence KE, Narr K, Sengupta B, Cooray G, Douglas DB, Thompson PM, McGough JJ, Bookheimer SY |title=Hemispheric brain asymmetry differences in youths with attention-deficit/hyperactivity disorder |journal=NeuroImage. Clinical |volume=18 |pages=744–752 |date=February 2018 |pmid=29876263 |pmc=5988460 |doi=10.1016/j.nicl.2018.02.020}}</ref>

[[Functional magnetic resonance imaging|Functional MRI]] (fMRI) studies have revealed a number of differences between ADHD and control brains. Mirroring what is known from structural findings, fMRI studies have shown evidence for a higher connectivity between subcortical and cortical regions, such as between the caudate and prefrontal cortex. The degree of hyperconnectivity between these regions correlated with the severity of inattention or hyperactivity<ref name="Damiani_2021">{{cite journal |vauthors=Damiani S, Tarchi L, Scalabrini A, Marini S, Provenzani U, Rocchetti M, Oliva F, Politi P |title=Beneath the surface: hyper-connectivity between caudate and salience regions in ADHD fMRI at rest |journal=[[European Child & Adolescent Psychiatry]] |volume=30 |issue=4 |pages=619–631 |date=April 2021 |pmid=32385695 |doi=10.1007/s00787-020-01545-0 |hdl-access=free |s2cid=218540328 |hdl=2318/1755224}}</ref> Hemispheric lateralisation processes have also been postulated as being implicated in ADHD, but empiric results showed contrasting evidence on the topic.<ref name="Tarchi_2022">{{cite journal |vauthors=Tarchi L, Damiani S, Fantoni T, Pisano T, Castellini G, Politi P, Ricca V |title=Centrality and interhemispheric coordination are related to different clinical/behavioral factors in attention deficit/hyperactivity disorder: a resting-state fMRI study |journal=Brain Imaging and Behavior |volume=16 |issue=6 |pages=2526–2542 |date=December 2022 |pmid=35859076 |pmc=9712307 |doi=10.1007/s11682-022-00708-8}}</ref><ref>{{cite journal |vauthors=Mohamed SM, Börger NA, Geuze RH, van der Meere JJ |title=Brain lateralization and self-reported symptoms of ADHD in a population sample of adults: a dimensional approach |journal=[[Frontiers in Psychology]] |volume=6 |page=1418 |date=2015 |pmid=26441789 |pmc=4585266 |doi=10.3389/fpsyg.2015.01418 |doi-access=free}}</ref>