ADHD is characterized by a pattern of behavior, present in multiple settings (e.g., school and home), that can result in performance issues in social, educational, or work settings. As in DSM-IV, symptoms will be divided into two categories of inattention and hyperactivity and impulsivity that include behaviors like failure to pay close attention to details, difficulty organizing tasks and activities, excessive talking, fidgeting, or an inability to remain seated in appropriate situations.Essential features:A. Persistent pattern of inattention and/or hyperactivity-impulsivity that is more frequently displayed and is more severe than is typically observed in individuals at comparable level of development.B. Some hyperactive-impulsive or inattentive symptoms must have been present before seven years of age.C. Some impairment from the symptoms must be present in at least two settings.D. There must be clear evidence of interference with developmentally appropriate social, academic or occupational functioning.E. The disturbance does not occur exclusively during the course of a Pervasive Developmental Disorder, Schizophrenia, or other Psychotic Disorders and is not better accounted for by another mental disorder.

Three Subtypes:Attention-Deficit/Hyperactivity Disorder Predominantly Inattentive Type:This subtype is used if six (or more) symptoms of inattention (but fewer than six symptoms of hyperactivity-impulsivity) have persisted for at least six months.Attention-Deficit/Hyperactivity Disorder Predominantly Hyperactive-Impulsive Type: This subtype should be used if six (or more) symptoms of hyperactivity-impulsivity (but fewer than six of inattention) have persisted for at least six months.Attention-Deficit/Hyperactivity Disorder Combined Type: This subtype should be used if six (or more) symptoms of inattention and six (or more) symptoms of hyperactivity-impulsivity have persisted for at least six months. Predominantly hyperactive-impulsive Most symptoms (six or more) are in the hyperactivity-impulsivity categories. Fewer than six symptoms of inattention are present, although inattention may still be present to some degree. Predominantly inattentive The majority of symptoms (six or more) are in the inattention category and fewer than six symptoms of hyperactivity-impulsivity are present, although hyperactivity-impulsivity may still be present to some degree. Children with this subtype are less likely to act out or have difficulties getting along with other children. They may sit quietly, but they are not paying attention to what they are doing. Therefore, the child may be overlooked, and parents and teachers may not notice that he or she has ADHD. Combined hyperactive-impulsive and inattentive Six or more symptoms of inattention and six or more symptoms of hyperactivity-impulsivity are present. Most children have the combined type of ADHD.Diagnostic Criteria for the three subtypes of Attention-Deficit/Hyperactivity Disorder according to DSM-IV:A. Persistent pattern of inattention and/or hyperactivity-impulsivity that is more frequently displayed and is more severe than is typically observed in individuals at comparable level of development. Individual must meet criteria for either (1) or (2):(1) Six (or more) of the following symptoms of inattention have persisted for at least six months to a degree that is maladaptive and inconsistent with developmental level:

Inattention(a) often fails to give close attention to details or makes careless mistakes in schoolwork, work or other activities(b) often has difficulty sustaining attention in tasks or play activity(c) often does not seem to listen when spoken to directly(d) often does not follow through on instructions and fails to finish schoolwork, chores or duties in the workplace (not due to oppositional behavior or failure to understand instructions)(e) often has difficulty organizing tasks and activities(f) often avoids, dislikes, or is reluctant to engage in tasks that require sustained mental effort (such as schoolwork or homework)(g) often looses things necessary for tasks or activities (e.g., toys, school assignments, pencils, books or tools)(h) is often easily distracted by extraneous stimuli(i) is often forgetful in daily activities(2) Six (or more) of the following symptoms of hyperactivity-impulsivity have persisted for at least six months to a degree that is maladaptive and inconsistent with developmental level:Hyperactivity(a) often fidgets with hands or feet or squirms in seat(b) often leaves seat in classroom or in other situations in which remaining seated is expected(c) often runs about or climbs excessively in situations in which it is inappropriate (in adolescents or adults, may be limited to subjective feelings of restlessness)(d) often has difficulty playing or engaging in leisure activities quietly(e) is often on the go or often acts as if driven by a motor(f) often talks excessivelyImpulsivity(g) often blurts out answers before questions have been completed(h) often has difficulty awaiting turn(i) often interrupts or intrudes on others (e.g., butts into conversations or games)B. Some hyperactive-impulsive or inattentive symptoms must have been present before age 7 years.C. Some impairment from the symptoms is present in at least two settings (e.g., at school [or work] and at home).D. There must be clear evidence of interference with developmentally appropriate social, academic or occupational functioning.E. The disturbance does not occur exclusively during the course of a Pervasive Developmental Disorder, Schizophrenia, or other Psychotic Disorders and is not better accounted for by another mental disorder (e.g., Mood Disorder, Anxiety Disorder, Dissociative Disorder, or a Personality Disorder).Signs & SymptomsInattention, hyperactivity, and impulsivity are the key behaviors of ADHD. It is normal for all children to be inattentive, hyperactive, or impulsive sometimes, but for children with ADHD, these behaviors are more severe and occur more often. To be diagnosed with the disorder, a child must have symptoms for 6 or more months and to a degree that is greater than other children of the same age.Children who have symptoms ofinattentionmay: Be easily distracted, miss details, forget things, and frequently switch from one activity to another Have difficulty focusing on one thing Become bored with a task after only a few minutes, unless they are doing something enjoyable Have difficulty focusing attention on organizing and completing a task or learning something new Have trouble completing or turning in homework assignments, often losing things (e.g., pencils, toys, assignments) needed to complete tasks or activities Not seem to listen when spoken to Daydream, become easily confused, and move slowly Have difficulty processing information as quickly and accurately as others Struggle to follow instructions.Children who have symptoms ofhyperactivitymay: Fidget and squirm in their seats Talk nonstop Dash around, touching or playing with anything and everything in sight Have trouble sitting still during dinner, school, and story time Be constantly in motion Have difficulty doing quiet tasks or activities.Children who have symptoms ofimpulsivitymay: Be very impatient Blurt out inappropriate comments, show their emotions without restraint, and act without regard for consequences Have difficulty waiting for things they want or waiting their turns in games Often interrupt conversations or others' activities.CausesScientists are not sure whatcausesADHD, although many studies suggest that genes play a large role. Like many other illnesses, ADHD probably results from a combination of factors.Genes.Results from several international studies of twins show that ADHD often runs in families. Researchers are looking at several genes that may make people more likely to develop the disorder.Children with ADHD who carry a particular version of a certain gene have thinner brain tissue in the areas of the brain associated with attention.Environmental factors.Studies suggest a potential link betweencigarette smokingand alcohol use during pregnancy and ADHD in children. In addition, preschoolers who are exposed to high levels of lead, which can sometimes be found in plumbing fixtures or paint in old buildings, may have a higher risk of developing ADHD.Brain injuries.Children who have suffered a brain injury may show some behaviors similar to those of ADHD. However, only a small percentage of children with ADHD have suffered a traumatic brain injury.Sugar.The idea that refined sugar causes ADHD or makes symptoms worse is popular, but more research discounts this theory than supports it. In one study, researchers gave children foods containing either sugar or a sugar substitute every other day.