Medical Conditions - Attention Deficit Hyperactivity Disorder

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Attention Deficit Hyperactivity Disorder

(ADHD, Attention Deficit Disorder, ADD)

The Facts

Attention deficit hyperactivity disorder (ADHD) is a disorder that is characterized by a pattern of inattention (inability to concentrate), and hyperactivity-impulsivity, that is persistent and developmentally inappropriate.

ADHD affects 4% to 12% of school-aged children, occurring more frequently in boys than girls. ADHD may persist into adulthood in many cases and is estimated to affect 3% to 4% of adults. 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  and social 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. It is also much more common in identical twins than in non-identical twins or siblings, and several genes associated with ADHD have been found.

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 sugar are sometimes blamed for causing ADHD. However, most experts do not think that ADHD can be caused by dietary factors.

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, home, or social life. Oftentimes, complaints about symptoms of ADHD will start from teachers, caregivers or parents.

Symptoms of ADHD fall into 2 large categories: inattention and hyperactivity – impulsivity.

The 9 inattentive symptoms are:

  • not paying attention to details or making careless mistakes
  • having difficulty sustaining attention
  • often not listening when spoken to directly
  • often not following through on assignments, or having trouble following instructions
  • having difficulty organizing tasks
  • often avoiding or disliking tasks that require sustained mental effort
  • often losing things
  • being easily distracted
  • forgetfulness

The 9 hyperactive-impulsive symptoms are:

  • often fidgeting or squirming
  • having difficulty remaining seated
  • often running and climbing when it is inappropriate (or for older individuals, feeling restless)
  • having difficulty playing quietly
  • often being “on the go” or acting as if “driven by a motor”
  • often talking excessively
  • blurting out answers to questions that have not been completed
  • having difficulty awaiting their turn
  • often interrupting or intruding

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

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

For some children, symptoms may dissipate as they grow older. However, many children with ADHD will continue to have symptoms into adulthood. Adults with ADHD may have slightly different symptoms. For example, they may feel extremely restless instead of being hyperactive (running, climbing, etc.). Adults may also have fewer symptoms, but will likely still have difficulty with paying attention and impulsivity.

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 and they must negatively affect social, academic or occupational functioning.

There are no specific blood tests, scans, or electronic tests of brain activity that are particularly helpful in making the diagnosis. A doctor determines whether the behavioural problems associated with the condition are a continuous problem that requires treatment. This should be done by interviewing the person, parents and teachers, and may be assisted by the use of questionnaires and rating scales.

To make the diagnosis, there must be at least 6 of the inattentive or hyperactive-impulsive symptoms present, and the following criteria must be met:

  • the symptoms should be present for over 6 months
  • at least some symptoms should have an onset before age 12
  • the symptoms must be present in at least 2 situations (such as home and school)
  • the symptoms must interfere with functioning at work, home, or school

For some people, ADHD may not be recognized and diagnosed until they are older adolescents or adults. People age 17 and older may have fewer symptoms and therefore require at least 5 rather than 6 symptoms of inattention or hyperactivity-impulsivity to be diagnosed.

Treatment and Prevention

It’s important to treat the condition. Untreated ADHD can seriously affect relationships, jobs, and school performance. 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 can include medication, behavioural therapies, changes at school or home, or a combination of these.

There are a number of medications for ADHD. These medications are very useful for treating the core symptoms of ADHD (e.g. hyperactivity, impulsiveness and inattention). Stimulants such as methylphenidate*, lisdexamfetamine, mixed salts amphetamine or dextroamphetamine 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, which helps to increase the levels of a neurotransmitter called norepinephrine in the brain. Note that all medications can have side effects. It is best to discuss the benefits and risks of a medication with your health care provider.

Some parents are wary of these medications. However, 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.

Non-medication treatments such as behavioural therapies, counselling and training for parents and teachers may also be used. 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. Behavioural therapies are particularly helpful for improving social interactions and behaviour (e.g. following rules, being motivated).

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 their 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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