Researchers have found that patients with different types of attention-deficit/hyperactivity disorder (ADHD) have impairments in unique brain systems, indicating that there may not be a one-size-fits-all explanation for the cause of the disorder. Based on performance on behavioral tests, adolescents with ADHD fit into one of three subgroups, where each group demonstrated distinct impairments in the brain with no common abnormalities between them.

https://www.sciencedaily.com/releases/2017/11/171107140834.htm