While all children and for that matter most adults suffer periodically from bouts of inattention, hyperactivity or impulsive behaviors, Attention-Deficit Hyperactivity Disorder (ADHD) is marked by behaviors that are inappropriate for one’s age.  While common in children and teens, ADHD can affect adults as well.  While the symptoms differ in adult ADHD, patients usually have problems with interpersonal relationships and in employment situations.  For someone to be diagnosed with ADHD, some symptoms must be present before the age of seven.  In addition, the symptoms must impair the patient’s ability to function appropriately in more than one setting (e.g. at home and at work or at home and at school).

What are the main symptoms of ADHD?
There are three different categories of symptoms: inattention, hyperactivity, impulsivity.

Inattention may manifest itself in the following ways:

• 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.

It is often difficult to find evidence of inattention until a child is put in a school environment.

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.

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.

ADHD is most commonly diagnosed after children display at least some of the above-mentioned behaviors consistently over a period of about a half a year in at least two different settings.

What is the long-term prognosis for those with ADHD?
A great many children with ADHD ultimately adjust. Approximately 20-30% of those diagnosed do develop some type of learning disability. Those ADHD sufferers with an associated conduct or oppositional-defiant disorder are more likely to drop out of school.
For the common patient diagnosed with ADHD, inattention tends to persist throughout childhood and adolescence and into adulthood, while the symptoms of hyperactivity and impulsivity tend to diminish with age.