Attention Deficit Hyperactivity Disorder

Source: MedlinePlus Health Topics, U.S. National Library of Medicine

Last synced 8/9/2026Status: primary verified

What is attention deficit hyperactivity disorder (ADHD)? ADHD is a neurodevelopmental disorder. It is usually first diagnosed in childhood and often lasts into adulthood. But some people don't get diagnosed with ADHD until they are adults. ADHD involves: Having trouble paying attention (inattention) Having trouble controlling impulsive behaviors (impulsivity) Being overly active (hyperactivity) What are the types of attention deficit hyperactivity disorder (ADHD)? There are three types of ADHD: Mostly Inattentive ADHD. People with this type of ADHD have trouble paying attention and are easily distracted. It's hard for them to organize or finish tasks. They may have trouble following instructions or conversations. Mostly Hyperactive-Impulsive ADHD. People with this type of ADHD have symptoms of both hyperactivity and impulsivity: With hyperactivity, people feel a need to always be moving. They have trouble sitting still and may fidget and/or talk too much. With impulsivity, people have trouble controlling their actions and words. They tend to act on sudden ideas or feelings without thinking about the possible results. They may interrupt others a lot or have trouble waiting their turn. Combined ADHD. People with this type of ADHD have a mix of inattentive and hyperactive-impulsive symptoms. Combined ADHD is the most common type. It's normal to sometimes have trouble paying attention or sitting still, especially for children. But people with ADHD have more severe symptoms that can sometimes cause serious problems, for example, failing grades for a child or a job loss for an adult. The symptoms are ongoing and may affect family and social life, too. What causes attention deficit hyperactivity disorder (ADHD)? The exact cause of ADHD is unknown. ADHD probably results from a combination of factors, such as genetics and your environment. Researchers are looking at possible environmental factors that might raise the risk of developing ADHD. These factors include brain injur

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This information is for general education and is not medical advice. Always talk to a licensed U.S. clinician about your situation, medications, or treatment decisions.