The Facts

Attention deficit hyperactivity disorder (ADHD) is a disorder that may be characterized by a pattern of inattention (inability to concentrate) sometimes combined with hyperactivity-impulsivity that is persistent, developmentally inappropriate, and occurs in at least 2 different settings before the age of 7.

ADHD affects 5% to 12% of school-aged children, occurring more frequently in boys than girls. ADHD may persist into adulthood in many cases. An inability to integrate in social, academic, or work-related settings is a pattern seen in people with a history of ADHD. In childhood, a person with ADHD may have academic problems, as the condition affects a person's ability to concentrate and focus on tasks. Because they are unable to organize their work or pay attention to their studies, children with ADHD may try to distract other children in class.

People with ADHD are especially sensitive to sensory stimuli such as noise, touch, and visual cues. They can easily be overstimulated, leading to changes in behaviour that may include aggressiveness.

Many people think ADHD and ADD (attention deficit disorder) are two different conditions, but they are in fact two names for the same condition. Other names no longer in use are minimal brain dysfunction (MBD) and hyperactivity.


Biological causes are at the root of ADHD. Specifically, neurological imbalances in the brain are thought to be responsible for the symptoms exhibited by a person with ADHD.

In the brain, chemicals called neurotransmitters help send messages throughout the body. Scientific studies show that certain neurotransmitters are lower in quantity or are lacking in people with ADHD.

Even though the neurological imbalances are present in people with ADHD, the exact cause is unclear. In many cases, ADHD appears to be largely genetic, since children with ADHD are four times more likely to have close family members with the same medical condition, and it is much more common in identical twins than in non-identical twins or siblings. Scientific research has not yet discovered the chromosomes that may be responsible for the condition.

During pregnancy or after birth, certain factors may damage the brain and alter its function. During pregnancy, exposure of the baby's developing brain to radiation, alcohol, or other factors may lead to this condition. Low birth weight may also increase the risk of ADHD. After birth, the development of certain infectious diseases that affect the brain tissue, such as meningitis or encephalitis, may affect the way the brain sends signals and contributes to the symptoms associated with ADHD.

Food additives and refined sugar are sometimes blamed for causing ADHD or making symptoms worse. There is no conclusive evidence to show that refined sugar worsens ADHD symptoms. Research suggests that artificial food colouring may increase hyperactive behavior among both hyperactive children and children from the general population.

Symptoms and Complications

An attention deficit problem is officially described as a disorder when it is developmentally inappropriate and the symptoms first appear before the age of 12 and significantly interfere with functioning in at least two settings including school, work, family, or social life.

Symptoms of a child with ADHD fall into 3 large categories: inattention, hyperactivity, and impulsivity.

The 9 inattentive symptoms are:

  • not paying attention to details
  • having difficulty sustaining attention
  • often not listening to what is said
  • often not following through on assignments, or having trouble following instructions
  • having difficulty organizing tasks
  • often avoiding tasks that require extra mental effort
  • often losing things
  • being easily distracted
  • forgetfulness

The 9 hyperactive-impulsive symptoms are:

  • fidgeting or squirming excessively
  • having difficulty remaining seated
  • often running and climbing when it is inappropriate
  • having difficulty playing quietly
  • often being “on the go” or acting as it “driven by a motor”
  • often talking excessively
  • blurting out answers to questions
  • having difficulty awaiting his or her turn in games
  • often interrupting or intruding

There's no official symptom list for adults, but symptoms are similar to those listed above.

People with ADHD are much more likely to experience a number of other nervous system disorders. These may include:

  • learning disabilities in 25% to 30% of children with ADHD despite normal intelligence
  • tic disorders (such as Tourette's syndrome) in 20% of children with ADHD – more than 50% of children with Tourette's are also diagnosed with ADHD
  • language problems, especially with expressive language (e.g., vocabulary)
  • oppositional defiant disorder
  • conduct disorder
  • autism
  • anxiety disorders (25%)
  • depression (20% to 30%)

Making the Diagnosis

ADHD is diagnosed on the basis of a combination of the symptoms listed above. These symptoms must interfere seriously with at least two major areas of a person's life, such as school, home, or another setting (e.g., an extracurricular activity). Also, the child must show these symptoms constantly for at least 6 months. There are no specific blood tests, scans, or electronic tests of brain activity that are particularly helpful in making the diagnosis. A specialist determines whether the behavioural problems associated with the condition are a continuous problem that requires treatment. This should be done with questionnaires and rating scales completed by the child's parents and teachers.

It's possible that people not diagnosed with ADHD may show the symptoms as adults. Studies show that many children with ADHD show signs of the condition in their adult lives.

Treatment and Prevention

It's important to treat the condition. Parents with children who have ADHD should not feel they've done something wrong if their child has trouble at school. People with ADHD are as intelligent and capable as anyone else and can lead happy, successful lives with the right help.

Treatment for ADHD usually consists of medication combined with educational, family, and other social changes.

There are a number of medications for ADHD. Note that all medications can have side effects. It is best to discuss the benefits and risks of medication with your health care provider. Stimulants such as methylphenidate*, lisdexamfetamine, or dextroamphetamine help to filter out unnecessary distractions in people who have ADHD. These medications stimulate the areas of the brain that do not have sufficient production of neurotransmitters to produce the needed chemicals. Another medication used to treat ADHD is called atomoxetine. It helps increase the levels of a neurotransmitter called norepinephrine in the brain allowing children to concentrate for longer periods of time and filter out distractions in their surroundings.

Some parents are wary of these medications, fearing that their child will become addicted or unable to succeed without chemical help. In fact, there's no evidence of addictiveness. Taking medication as prescribed, whether short- or long-term, may help children maintain a high level of function that may not be possible without the medication. Some children, especially those with coexisting problems or disorders (see the list in "Symptoms and Complications" above) may require other types of medication. Some children may manage without medication.

Medications should be accompanied by supportive counselling, and possibly sessions with a specialist such as a psychiatrist or a psychologist. Parent training in effective child behaviour management methods, classroom behaviour modification methods, and academic interventions such as special educational placement, have all shown promising results. Some modern behaviour modification and cognitive behavioural therapy produces successful results in children with ADHD without the use of medication. Changes in diet have not been shown to help in the treatment of individuals with ADHD.

To complement their other treatments, people with ADHD can benefit from a healthy lifestyle including regular exercise, proper nutrition, and good sleep habits (such as going to bed and waking up at consistent times and avoiding caffeine, large meals, and stressful activities before bed).

Overall, once a treatment is in place, children with ADHD need to learn to use their newfound concentration to the best advantage.

*All medications have both common (generic) and brand names. The brand name is what a specific manufacturer calls the product (e.g., Tylenol®). The common name is the medical name for the medication (e.g., acetaminophen). A medication may have many brand names, but only one common name. This article lists medications by their common names. For information on a given medication, check our Drug Information database. For more information on brand names, speak with your doctor or pharmacist.

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