ADHD is one of the most common neurodevelopmental disorders. One out of every twenty-one people in Canada has the disorder. Although some children can grow out of ADHD, the majority of children who are diagnosed with ADHD still have it as teens and into adulthood.

Children and youth with ADHD have challenges with regulating their attention (having too much or too little focus). Many children and youth with ADHD also struggle with restlessness and impulsivity (having impulsive actions, thoughts, or feelings).

ADHD is diagnosed in males more than females, especially for children who have higher levels of impulsivity and hyperactivity.

ADHD causes a variety of problems in young children, but is usually only diagnosed after they start school. Some children manage to cope with the symptoms, but during teen years as the hormonal changes of adolescence are going on and the demands of school and extracurricular activities are increasing, ADHD symptoms may get worse.

The cause of ADHD is not fully understood, but research shows in most cases it is thought to have a genetic component as it runs in families. Scientists have shown that there are differences in the brain size, networks, neurotransmitters, and brain development of children with ADHD, but they do not fully understand how these lead to the cause and the symptoms of ADHD. 
The environment may also play a role (for example, prenatal exposure to toxins or premature birth). Diet, video game use, and parenting style do not cause ADHD.

There are two groups of ADHD symptoms - inattentive symptoms and hyperactive/impulsive symptoms. Most children and youth living with ADHD have some symptoms from both groups.

 A child or youth with inattentive symptoms may:have a hard time staying focused on tasks they find boring
make unintentional mistakes at school 
appear not to be listening when spoken to
have a hard time following directions
lose or misplace things
have difficulty organizing thoughts or belongings
dislike tasks where they have to be focused for a longer time
appear forgetful

A child or youth with hyperactive/impulsive symptoms may:have problems sitting still
look very restless or fidget often
have a hard time playing quietly
climb and run a lot 
seem to be always 'on the go'
talk too much
blurt out answers before you finish a question
interrupt tasks or conversations
have a hard time waiting for their turn

​Other conditions that can exist along with ADHD include:anxiety disorders
mood disorders like depression
specific learning disorder
autism spectrum disorder
developmental coordination disorder
sensory processing difficulties
oppositional defiant disorder
substance use challenges