ADHD is a persistent pattern of inattention and/or hyperactivity-impulsivity that interferes with functioning. It was first described in 1902 and its name and classification have evolved. There are three main types: inattentive, hyperactive-impulsive, and combined. Symptoms include inattention, hyperactivity, and impulsivity. ADHD affects about 3-5% of children globally and is diagnosed more in boys than girls. Causes are unclear but genetics and brain function play a role. Treatments include medication, therapy, diet, and lifestyle changes. Proper diagnosis requires symptoms in multiple environments and contexts according to diagnostic criteria. However, some studies suggest overdiagnosis may occur.