Attention Deficit Hyperactivity Disorder

Scientists agree that ADHD is a medical neurobiological disorder. It is an illness or deficit of the nervous system most often due to genetic or biological factors. Family, twin and adoption studies have found that heredity is the most common cause of ADHD. If a child has ADHD there is five times more likelihood that another family member will also have the disorder. While ADHD symptoms may be caused by injury to the brain, or exposure to alcohol, nicotine or lead in the developing brain (in utero), this is not the cause in the vast majority of children with ADHD.

ADHD is not new; it has been described in literature and medically documented for more than two centuries. ADHD is a chronic condition that can present at all levels of severity and rarely occurs by itself. There are three core symptoms: the inability to regulate attention, the inability to regulate activity, and difficulty with inhibitory behavior resulting in impulsivity. However, difficulty with regulating emotions is often an issue as well.  It is important to note that symptoms of ADHD can vary from day to day and hour to hour, and while many children and adults may exhibit these symptoms, it is the degree of presentation, the inability to regulate them and the level of impairment, that results in a diagnosis. Symptoms must be at a level that impairs daily functioning for ADHD to be diagnosed.

How Do Executive Functions Play a Role in ADHD?

New research has shown us that children and adults with ADHD often have weaknesses in the areas of executive functioning (EF). Executive functioning is the mental process that allows us to plan ahead, evaluate the past, start and finish a task and manage our time. Executive functioning skills enable us to: identify a problem, find solutions, organize ourselves, regulate our behaviour and emotions, control our attention levels and resist distractions. Working memory, an important part of executive functioning, is a skill that allows us to keep information in the brain and manipulate it at the same time. Working memory directly impacts reading comprehension, written expression, math skills and the ability to pay attention and resist distraction. Students with ADHD also frequently process information coming in and going out at a slower or inconsistent speed. Children with deficits in these areas are frequently mislabeled as being unmotivated, defiant, and lazy.

For more information on Executive Functioning please access the document with this title, or access information on the CADDAC web site.

How Often Does ADHD Occur?

ADHD is the most common mental health disorder of childhood. Studies throughout the world have reported the occurrence of ADHD in school age children as being between 5% and 12%. This means that on average there are at least one to three children in every class with ADHD. More boys than girls are diagnosed at a rate of 3 to 1. However, since girls are less likely to display outward hyperactivity and impulsivity, and as many women as men are diagnosed in adulthood, we know that we still miss diagnosing many girls with ADHD in childhood. However, females with ADHD are equally impaired in the areas of attention regulation and struggle just as much as males with social and academic problems. Eighty per cent of adolescents who were diagnosed as children continue to meet the criteria for diagnosis, and of those children, over sixty per cent report continued impairing symptoms into adulthood.

Are There Different Types of ADHD?

Until the recent DSM-5 ADHD was classified into three subcategories based upon the clustering of three core symptoms. Children and adults who only have hyperactive and impulsive symptoms were diagnosed as “ADHD, primarily hyperactive-impulsive subtype” (very rare); those who display significant impairment in inattention were referred to as “ADHD, primarily inattentive subtype” (formerly known as ADD), and those who display all three symptom clusters were referred to as “ADHD, combined subtype” (the most common).  The new DSM-5 no longer recognizes these sub-types because they are unstable across time and often invalid. The new DSM believes they are best understood to be variations in the current manifestation, so are now referred to as different presentations.