What is attention deficit hyperactivity disorder?
Attention deficit hyperactivity disorder (ADHD) is a neurodevelopmental condition (a condition that causes subtle differences in the brain). It mainly involves difficulties with:
- controlling attention
- regulating behaviour and activity levels (impulsivity/hyperactivity)
When left untreated, ADHD can lead to difficulties with school performance, self-control, memory, emotions, friendships, relationships with family and other areas of life.
What causes ADHD?
The exact causes of ADHD are not known. However, two factors associated with the disorder are genetics and environmental factors.
Genetics
ADHD runs in families. A child with ADHD is likely to have a sibling or parent with ADHD. When a doctor diagnoses ADHD in a child, it is not uncommon for parents to suspect that a parent or another child may also have the disorder. That being said, there is currently no genetic test to confirm or rule out a diagnosis of ADHD.
Genetic causes differ for each child. Researchers are now studying:
- how genes work together
- how genes interact with environmental factors to influence behaviour
- how genes influence responses to treatment
Environmental factors
Environmental factors that play a role in ADHD include:
- alcohol use in pregnancy
- prematurity or low birth weight
- exposure to lead or other toxins
Other environmental factors can worsen symptoms of ADHD. These include family stressors such as:
- financial difficulties
- exposure to violence
- family breakup with ongoing animosity (or hostility)
- harsh or inconsistent parenting
- inconsistent supervision or support, for example if a caregiver cannot supervise a child properly because of their own physical or mental health challenges
How common is ADHD?
On average, ADHD affects 5 per cent of school-aged children around the world, or about one in every 20 children. ADHD also affects about 4 per cent of adults, or about one adult in 25.
ADHD is more common in boys than in girls. It is often easier to recognize and diagnose ADHD in boys because they tend to be more active. Girls with ADHD may be more likely to be overlooked because their symptoms are less obvious even though they may have as much difficulty as boys with academic and social skills.
Does ADHD occur with other conditions?
ADHD can occur with other conditions such as:
- autism spectrum disorder
- speech and language difficulties
- specific learning difficulties
- Tourette’s syndrome and other tic disorders (conditions that cause short, sudden and repeated movements or sounds)
- epilepsy
- developmental co-ordination disorder (DCD) (suspected when a child’s co-ordination is poorer than expected for their age and intelligence)
- acquired brain injury
Children with ADHD may sometimes also have mental health conditions such as anxiety, mood disorders (such as depression or bipolar disorder) or behaviour disorders. These can affect school performance and lead to problems in the teen years.
ADHD has also been linked with longstanding sleep difficulties.
About two-thirds of children with ADHD have at least one other condition. It is important to understand if a child has another condition alongside ADHD as it may affect diagnosis and treatment.
When to see a health-care provider about ADHD
See your child’s health-care provider if you suspect your child may have ADHD. You can find out more in the page about ADHD signs and symptoms.
If your child is diagnosed with ADHD, their health-care provider can review parenting approaches and, depending on your child’s age, discuss medication treatments.
Further information
For more information on ADHD, please see the following pages:
ADHD: How to help your child at home
ADHD: Communicating with your child's school
ADHD: Treatment with medications
Resources
The following resources offer support and additional information about ADHD.
Websites
Learning Disabilities Association of Ontario
Centre for ADHD Awareness, Canada - CADAC
Journal articles
Heinonen, K. et al (2010). Behavioural symptoms of attention deficit/hyperactivity disorder in preterm and term children born small and appropriate for gestational age: A longitudinal study. BMC Pediatrics. Dec 15 2010 10:91. doi: 10.1186/1471-2431-10-91.
Sucksdorff, M. et al (2015). Preterm Birth and Poor Fetal Growth as Risk Factors of Attention-Deficit/ Hyperactivity Disorder. Pediatrics Sept 2015 136 (3) e599-e608. doi:10.1542/peds.2015-1043.