There are three types of ADHD, according to the National Institute of Mental Health (NIMH). The "Predominately Inattentive" subtype (ADHD-PI) occurs when a person only has the core symptom of inattention; this subtype used to be called ADD. When a person has the core symptoms of hyperactivity and impulsivity, he has the "Hyperactive-Impulsive" type (ADHD-HI). Most often, though, people have all three core symptoms, meeting criteria for the "Combined" type (ADHD-C).
Inattention
Signs of inattention include inability to follow through on activities, problems with organization, and failure to pay attention to details. People with ADHD-level inattention are frequently forgetful and easily distracted from the tasks they're working on, the Mayo Clinic says. They also tend to often lose items that they need to complete a task, such as the calculator they are using for math homework or the wrench they are using to fix the kitchen sink. To be diagnosed with ADHD, the core symptom(s) must impair a person's ability to function, says KidsHealth.org. In other words, everyone is forgetful, distracted and unorganized at times, so psychologists are only concerned when these symptoms occur frequently and in a way that disrupts school or work. In addition, the symptoms must have been present before seven years of age in order for ADHD to be diagnosed, even if the actual diagnosis does not come until years or decades later. Finally, the individual must exhibit the symptoms in at least two different settings, the NIMH says. For example, a child who cannot pay attention at school but who does fine at home probably does not have ADHD. Instead, he is reacting to the school environment, a problem that should be investigated further.
Hyperactivity
People with ADHD-level hyperactivity never seem to stop. When they are supposed to be sitting, they are squirming, fidgeting or leaping out of their chairs, according to the Mayo Clinic. They tend to talk rapidly and in greater quantity than most people. They also do not like quiet, leisure activities, whether it be calm play with dolls or trucks during childhood or reading on a hammock during adulthood. Children with ADHD may also run and climb excessively, never seeming to tire out, says the NIMH. To meet diagnostic criteria for ADHD, symptoms must have been present for at least six months. This rules out the many short-lived reasons for hyperactivity, such as stress in the home or school environment. ADHD is a stable internal disorder, not a cluster of symptoms that come and go.
Impulsivity
The final core symptom of ADHD is impulsivity. This symptom is shown through problems waiting for one's turn, interrupting others while they are still speaking, and answering questions prematurely, the Mayo Clinic says. A person with ADHD-level impulsivity always seems to be jumping ahead, eager to get three steps beyond where a conversation or situation is currently situated, according to the NIMH.
