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 5% to 9% 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 5% of adults. An inability to integrate in social, academic, or work-related settings is a pattern seen in people with a history of ADHD. A person with ADHD may have academic and social problems as the condition affects a person's ability to concentrate and focus on tasks.

People with ADHD are especially sensitive to sensory stimuli such as noise, touch, and visual cues. They may often feel overstimulated emotionally as well.

A common belief is that ADHD and ADD (attention deficit disorder) are 2 different conditions, but these names are in fact used interchangeably for the same condition. The term ADD was previously the official name for the disorder; the name ADHD, which includes an “H” for “hypersensitivity”, is now the official name for the disorder.


While specific causes of ADHD have yet to be identified, it appears to be largely genetic. Children with ADHD are 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.

Factors such as parenting style, exposure to television at a young age, or diet are sometimes blamed for causing ADHD. However, there’s limited evidence that these factors are related to ADHD.

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. The symptoms should also not be likely caused by other types of mental health conditions like a mood or anxiety disorder.

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 mental, emotional, or behavioral disorders. These may include:

  • autism spectrum disorders
  • anxiety disorders
  • depression
  • behavioral issues, or oppositional defiant disorder
  • learning disorders, such as difficulty with reading, writing, or mathematics
  • sleep disorders

For some children, symptoms may dissipate as they grow older. However, many children with ADHD will continue to have symptoms into adulthood. ADHD symptoms can also persist into older adulthood, where they can often be confused with other symptoms seen as part of the normal aging process or from conditions like dementia.

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 person 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 in children up to 16 years of age, 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
  • the symptoms are not affected or better explained by another mental health disorder, such as an anxiety disorder, a personality disorder, or schizophrenia.
  • at least some symptoms should have been present before age 12
  • the symptoms are present in at least 2 situations (such as home and school)
  • the symptoms are interfering with their functioning at work, home, or school

For some people, ADHD may not be recognized and diagnosed until they are older adolescents or adults. People who are 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.

Because people with ADHD can have inattentive and/or hyperactive-impulsive symptoms, this condition can be grouped into 3 main types:

  • Combined (symptoms of both inattention and hyperactivity-impulsivity)
  • Predominantly inattentive (mostly symptoms of inattention)
  • Predominantly hyperactive-impulsive (mostly symptoms of hyperactivity-impulsivity)

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.

Treatments for ADHD include medication, behaviour management, changes at school or home, or a combination of these.

For children with ADHD, getting trained in child behavior management methods, classroom behavior modification methods, and school-based interventions such as special educational placement, have all shown promising results. Behavioral therapies are particularly helpful for improving social interactions and behavior (e.g., following rules, being motivated).

For individuals who were diagnosed with ADHD later in life, learning more about the condition and getting information is often helpful. Health care providers like occupational therapists, ADHD coaches, and support groups can help them make lifestyle changes that help reduce the impact of ADHD in their daily life. There are also vocational assessment services available to help those with ADHD obtain appropriate workplace accommodations.

There are a number of medications for ADHD which can be used for those aged 6 years and older. 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 ADHD medications can have side effects such as a decreased appetite or sleep disturbances. It is best to discuss the benefits and risks of a medication with your health care provider.

Many people may be wary of these medications. However, taking medication as prescribed, whether short- or long-term, may help those living with ADHD to maintain a high level of function that may not be possible without the medication. Some individuals, especially those with coexisting problems or disorders (see the list in "Symptoms and Complications" above) may require other types of medication. Other individuals may manage without medication.

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).

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