What is attention deficit hyperactivity disorder ( ADHD )?

ADHD is a behavioral disorder that may begin in early childhood and often lasts through adolescence and adulthood. Because no one yet knows the true cause of ADHD (though many experts now believe it's a brain chemistry problem), the easiest way to define it is by describing its main symptoms. Children with ADHD consistently have short attention spans, difficulty controlling their impulses, and are often hyperactive or physically restless. Symptoms can start as early as age 3, but most children cannot be diagnosed until age 7, since many symptoms of the condition are within the range of normal behavior in young children.

Not all children with ADHD display the same symptoms. For this reason, health professionals have identified three main types of ADHD:

Primarily inattentive
Children repeatedly fail to finish tasks, can't concentrate and get distracted easily, and seem not to listen. You may notice your child daydreaming a lot. Children with inattentive ADHD are not hyperactive. This is the main type of ADHD found in girls. It's sometimes referred to as ADD or attentive deficit disorder.

Primarily hyperactive / impulsive
Children fidget and squirm constantly and can't wait their turn. They often act without thinking things through. Children with hyperactive / impulsive ADHD are often quite capable of paying attention. This type of ADHD is most often found in preschool-age children.

A combination of inattentive and hyperactive / impulsive
Children show signs of both types of ADHD. This is the most common form of ADHD among school-age children.

If you're the parent of a preschooler, these behaviors probably sound familiar. Almost all children occasionally get overexcited and spacey. That's part of what makes diagnosing ADHD difficult. But a child with ADHD will be more easily distracted and more impulsive than most kids, and his activity level may border on the frenetic. He'll also show these symptoms repeatedly for at least six months and they'll have a negative effect on at least two areas of his life — at home, at school, or with friends, for instance.

How common is ADHD?
According to the American Academy of Pediatrics, ADHD affects 4 to 12 percent of U.S. schoolchildren. Studies indicate that ADHD affects three times as many boys as girls, and there is often a strong family history of other males with the condition. Girls are more likely to be diagnosed with the inattentive form of ADHD.

What causes ADHD?
Most researchers now believe that ADHD has a genetic basis: If one person in a family has ADHD, there's a 25 to 35 percent chance that another family member also has it.

They also believe that ADHD has a neurological cause. It seems likely that people with ADHD inherit a physical inability to regulate levels of neurotransmitters (substances that transmit signals in the brain), such as dopamine.

Contrary to what you may have heard, ADHD is not caused by poor parenting, family problems, bad teachers or schools, or too much TV. In the past, researchers wondered whether drug or alcohol abuse by the mother during pregnancy or psychological trauma early in a child's life might cause ADHD. But these hypotheses don't account for the vast majority of children with ADHD whose mothers didn't use harmful substances and who didn't go through hard times as babies.

For a time researchers also theorized that attention disorders were caused by minor head injuries or damage to the brain (and for many years ADHD was called "minimal brain damage" or "minimal brain dysfunction"). But the vast majority of people with ADHD have no history of head injury or evidence of brain damage.

You may also have heard that refined sugar and food additives make children hyperactive and inattentive. But scientists at the National Institutes of Health (NIH) concluded that this may apply to only about 5 percent of children with ADHD, mostly either very young children or children with food allergies.

What are the symptoms of ADHD?
To be true symptoms of ADHD, the following should be present in more than one setting, such as at home and in school, and the behaviors must adversely affect a child's functioning in school or social situations.

Inattentive ADHD
A child must exhibit six of the following symptoms for at least six months:
 

• Often fails to give close attention to details or makes careless mistakes in schoolwork or other activities

• Often has trouble sustaining attention for tasks or play

• Often doesn't seem to listen to what's being said to him

• Often doesn't follow through on instructions and fails to finish schoolwork or chores (not out of rebellion or failure to understand)

• Often has difficulty organizing tasks and other activities

• Avoids or strongly dislikes tasks (such as schoolwork or homework) that require sustained mental effort

• Often loses things necessary for tasks or activities (such as toys, school assignments, pencils, and books)

• Is easily distracted by the world around him

• Is often forgetful

Hyperactive / impulsive ADHD
A child must exhibit six of the following symptoms for at least six months:
 

• Often fidgets with hands or feet or squirms when seated

• Leaves his seat in the classroom or in other situations in which remaining seated is expected

• Often runs around or climbs in situations where it is inappropriate

• Often has difficulty playing quietly

• Often talks excessively

• Often on the go or acts as if driven by a motor

• Often blurts out answers before the whole question has been stated

• Often has difficulty waiting in lines or waiting for his turn in group play

• Often interrupts or intrudes on others' conversations or games, for instance

Combined Type ADHD
A child must exhibit six behaviors in both the inattentive and hyperactive / impulsive lists above for at least six months.

When should I seek help?
Make an appointment with your pediatrician if your child is unusually impulsive or frequently seems unable to listen, to the point where it is affecting his ability to get along at home, daycare, or school. For example, if his daycare provider or teacher tells you that your child consistently can't get halfway through a project or sit still for a story, or disrupts other children who are trying to participate, you have cause for concern. The doctor will evaluate your child and decide whether further testing or a visit to a specialist is necessary.

Of course, these kinds of behavior don't necessarily mean that your child will be diagnosed with ADHD. A hearing or vision problem or an emotional situation such as a death or divorce in the family could be challenging his concentration, or he could simply need more outlets for physical activity.