In adults, ADHD symptoms must be present since childhood and affect the person’s ability to function in daily life. These symptoms must create significant difficulty in at least two areas of life, such as home, social settings, school, or work.
Increasingly, researchers are studying ADHD in the context of executive functions—the brain functions that activate, organize, integrate, and manage other functions. Impairment of these executive functions is considered highly interrelated to symptoms associated with ADHD.
There are three primary subtypes of ADHD, each associated with different symptoms.
Research has demonstrated that ADHD has a very strong neurobiological
basis. Although precise causes have not yet been identified, there is
little question that heredity makes the largest contribution to the
expression of the disorder in the population.
In instances where heredity does not seem to be a factor,
difficulties during pregnancy, prenatal exposure to alcohol and tobacco, premature delivery, significantly low birth weight, excessively high body lead levels, and postnatal injury to the prefrontal regions of the
brain have all been found to contribute to the risk for ADHD to varying
HAVE QUESTIONS? We can help.
Learn more about ADHD and related conditions at CHADD’s
National Resource Center on ADHD. You
may also contact us by phone (800-233-4050) and use our Online Form (select "Questions about ADHD") and a health information
specialist will provide a personalized response.
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