The symptoms of ADHD include inattention and/or hyperactivity and impulsivity. These are traits that most children display at some point or another. But to establish a diagnosis of ADHD, sometimes referred to as ADD, the symptoms should be inappropriate for the child's age.

ADHD is common in children and teens. Adults also can have ADHD. With ADHD in adults, there may be some variation in symptoms. For instance, an adult may experience restlessness instead of hyperactivity. In addition, adults with ADHD consistently have problems with interpersonal relationships and employment.

There are three different types of ADHD, including:

• combined ADHD (the most common type), which involves all of the symptoms
• inattentive ADHD (previously known as ADD), which is marked by impaired attention and concentration
• hyperactive-impulsive ADHD, which is marked by hyperactivity without inattentiveness

For a diagnosis of ADHD, some symptoms that cause impairment must be present before age seven. Also, some impairment from the symptoms must be present in more than one setting. For instance, the person may be impaired at home and school or home and work. Also, there must be clear evidence the symptoms interfere with the person's ability to function at home, in social environments, or in work environments.

There are three different categories of ADHD symptoms: inattention, hyperactivity, impulsivity.

Inattention may not become apparent until a child enters the challenging environment of school. In adults, symptoms of inattention may manifest in work or in social situations.

A person with ADHD may have some or all of the following symptoms:

• difficulty paying attention to details and tendency to make careless mistakes in school or other activities; producing work that is often messy and careless
• easily distracted by irrelevant stimuli and frequently interrupting ongoing tasks to attend to trivial noises or events that are usually ignored by others
• inability to sustain attention on tasks or activities
• difficulty finishing schoolwork or paperwork or performing tasks that require concentration
• frequent shifts from one uncompleted activity to another
• procrastination
• disorganized work habits
• forgetfulness in daily activities (for example, missing appointments, forgetting to bring lunch)
• failure to complete tasks such as homework or chores
• frequent shifts in conversation, not listening to others, not keeping one's mind on conversations, and not following details or rules of activities in social situations

Hyperactivity symptoms may be apparent in very young preschoolers and are nearly always present before the age of seven. Symptoms include:

• fidgeting, squirming when seated
• getting up frequently to walk or run around
• running or climbing excessively when it's inappropriate (in teens this may appear as restlessness)
• having difficulty playing quietly or engaging in quiet leisure activities
• being always on the go
• often talking excessively

Hyperactivity may vary with age and developmental stage.

Toddlers and preschoolers with ADHD tend to be constantly in motion, jumping on furniture, and having difficulty participating in sedentary group activities. For instance, they may have trouble listening to a story.

School-age children display similar behavior but with less frequency. They are unable to remain seated, squirm a lot, fidget, or talk excessively.

In adolescents and adults, hyperactivity may manifest itself as feelings of restlessness and difficulty engaging in quiet sedentary activities.

Impulsivity symptoms include:

• impatience
• difficulty delaying responses
• blurting out answers before questions have been completed
• difficulty awaiting one's turn
• frequently interrupting or intruding on others to the point of causing problems in social or work settings
• initiating conversations at inappropriate times

Impulsivity may lead to accidents such as knocking over objects or banging into people. Children with ADHD may also engage in potentially dangerous activities without considering the consequences. For instance, they may climb to precarious positions.

Many of these symptoms occur from time to time in normal youngsters. However, in children with ADHD they occur frequently -- at home and at school or when visiting with friends. They also interfere with the child's ability to function normally.

ADHD is diagnosed after children consistently display some or all of the above behaviors in at least two settings, such as at home and in school, for at least six months.

Quick GuideADHD/ADD in Adults: Symptoms & Treatments in Pictures

Some children with ADHD -- approximately 20% to 30% -- develop learning problems that may not improve with ADHD treatment. Hyperactive behavior can be associated with the development of other disruptive disorders, particularly conduct and oppositional-defiant disorder. Why this association exists is not known.

A great many children with ADHD ultimately adjust. Some, though, especially those with an associated conduct or oppositional-defiant disorder, are more likely to drop out of school. These individuals fare more poorly in their later careers than individuals who did not have ADHD do.

Inattention tends to persist through childhood and adolescence and on into adulthood. The symptoms of hyperactivity and impulsivity tend to diminish with age.

As they grow older, some teens that have had severe ADHD since middle childhood experience periods of anxiety or depression.

There are several warning signs for ADHD that seem to get worse when demands at school or home increase. They include:

• difficulties following instructions
• being unable to get organized, either at home or at school
• fidgeting, especially with the hands and feet
• talking too much
• failing to finish projects, including chores and homework
• not paying attention to and responding to details
• getting poor grades in school
• being isolated from peers due to poor grades and secondary depression

WebMD Medical Reference