The cause of ADHD is largely genetic. There is no compelling evidence indicating that social factors, such as parenting or educational environment, have been found to cause ADHD. Research has also ruled out diet, TV or media consumption, or videogame play as contributing factors.

Roughly ten percent of your students are likely to have ADHD. Numbers for this are hard to pin down exactly: The National Institute of Mental Health puts the total number of children and adolescents diagnosed with ADHD at about 11%, the CDC at 9.4%, and Barkley at 5 to 8%. Regardless of the source, the numbers continue to rise every year, and boys have a higher rate of diagnosis than girls. More important than an exact number is this: Every year, you should expect to have at least a few students in your classroom who have ADHD.

Rates of diagnosis do not necessarily reflect the actual number of students with ADHD. Barkley says diagnoses tend to occur more in communities with more resources, and overdiagnosis is more frequent “in upper income neighborhoods where a premium is placed on academic excellence or acceleration” (p. 8). By contrast, students may be underdiagnosed in communities with fewer resources for diagnosis and treatment. Apart from just being good general knowledge to have, this may inform the research and action you take depending on the community where you teach: Perhaps more of your students actually need to be referred for diagnosis and treatment; by contrast, you may be working with students who are receiving treatment for a misdiagnosis.