The three people you've just met, Mark, Lisa, and Henry, all have a form of ADHD (Attention Deficit Hyperactivity Disorder). ADHD is not like a broken arm, or strep throat. Unlike these two disorders, ADHD does not have clear physical signs that can be seen in an x-ray or a lab test. ADHD can only be identified by looking for certain characteristic behaviors, and as with Mark, Lisa, and Henry, these behaviors vary from person to person. Scientists have not yet identified a single cause behind all the different patterns of behavior--and they may never find just one. Rather, someday scientists may find that ADHD is actually an umbrella term for several slightly different disorders.

At present, an ADHD diagnosis is applied to children and adults who consistently display certain characteristic behaviors over a period of time. The most common ADHD behaviors fall into three categories: inattention, hyperactivity, and impulsivity.

Inattention. People who are inattentive have a hard time keeping their mind on any one thing and may get bored with a task after only a few minutes. They may give effortless, automatic attention to activities and things they enjoy. But focusing deliberate, conscious attention to organizing and completing a task or learning something new is difficult.

For example, Lisa found it agonizing to do homework. Often, she forgot to plan ahead by writing down the assignment or bringing home the right books. And when trying to work, every few minutes she found her mind drifting to something else. As a result, she rarely finished and her work was full of errors.

Hyperactivity. People who are hyperactive always seem to be in motion. They can't sit still. Like Mark, they may dash around or talk incessantly. Sitting still through a lesson can be an impossible task. Hyperactive children squirm in their seat or roam around the room. Or they might wiggle their feet, touch everything, or noisily tap their pencil. Hyperactive teens and adults may feel intensely restless. They may be fidgety or, like Henry, they may try to do several things at once, bouncing around from one activity to the next.

Impulsivity. People who are overly impulsive seem unable to curb their immediate reactions or think before they act. As a result, like Lisa, they may blurt out inappropriate comments. Or like Mark, they may run into the street without looking. Their impulsivity may make it hard for them to wait for things they want or to take their turn in games. They may grab a toy from another child or hit when they're upset.

Not everyone who is overly hyperactive, inattentive, or impulsive has an attention disorder. Since most people sometimes blurt out things they didn't mean to say, bounce from one task to another, or become disorganized and forgetful, how can specialists tell if the problem is ADHD?

To assess whether a person has ADHD, specialists consider several critical questions: Are these behaviors excessive, long-term, and pervasive? That is, do they occur more often than in other people the same age? Are they a continuous problem, not just a response to a temporary situation? Do the behaviors occur in several settings or only in one specific place like the playground or the office? The person's pattern of behavior is compared against a set of criteria and characteristics of the disorder. These criteria appear in a diagnostic reference book called the DSM (short for the Diagnostic and Statistical Manual of Mental Disorders).

According to the diagnostic manual, there are three patterns of behavior that indicate ADHD. People with ADHD may show several signs of being consistently inattentive. They may have a pattern of being hyperactive and impulsive. Or they may show all three types of behavior.

According to the DSM, signs of inattention include:

• becoming easily distracted by irrelevant sights and sounds
• failing to pay attention to details and making careless mistakes
• rarely following instructions carefully and completely
• losing or forgetting things like toys, or pencils, books, and tools needed for a task

Some signs of hyperactivity and impulsivity are:

• feeling restless, often fidgeting with hands or feet, or squirming
• running, climbing, or leaving a seat, in situations where sitting or quiet behavior is expected
• blurting out answers before hearing the whole question
• having difficulty waiting in line or for a turn

next: Other Conditions With Symptoms Similar to ADHD

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Reviewed: 01/2006