ADHD is a neurobiological disorder affecting approximately 11% of children, and is seen in countries all over the world. It is a highly heritable condition, about 80% genetically determined, which is almost as heritable as human height! Environmental influences are also thought to play a role.
ADHD is characterized by difficulties in three core areas: Inattention, Impulsivity and Hyperactivity, per the DSM-5 diagnostic criteria. However, there are other common features seen that are not included the criteria, including problems with emotional regulation, working memory and reward systems.
About two thirds of patients with ADHD will have a comorbid (coexisting) disorder, such as a learning disorder, anxiety, depression, oppositional defiant disorder, autism spectrum disorder or sleep problem. Most children diagnosed with ADHD will have symptoms that persist into adulthood.