Due to the complexity of this disorder, ADHD cannot be attributed to a single cause but probably results from a combination of different factors. However, research has identified that the primary causes of ADHD are genetic (76% heritability) and environmental (traumatic brain injury experienced in childhood, central nervous system infections, prematurity, hypoxic-ischemic encephalopathy or fetal exposure to toxic substances during pregnancy).
This disorder is characterized by the core symptoms of inattention and/or hyperactivity-impulsivity. There are subtypes of ADHD based on the predominant symptom (attention deficit or hyperactivity-impulsivity) or on whether the symptoms appear combined.
The main signs of each category are:
Inattention:
– Fails to pay attention to details and makes careless mistakes
– Has problems sustaining attention in tasks or fun activities
– Is easily distracted by extraneous stimuli
– Does not seem to listen when spoken to directly
– Has difficulty following through on instructions and fails to finish tasks
– Has trouble organizing tasks and activities
– Avoids tasks that require sustained mental effort
– Is forgetful in daily activities
Hyperactivity:
– Fidgets with hands or feet or squirms in seat
– Leaves seat in situations in which remaining seated is expected
– Has excess energy
– Runs about or climbs excessively in situations where it is inappropriate (in adults, feelings of restlessness)
– Has trouble playing or engaging in leisure activities quietly
– Talks excessively
Impulsivity:
– Blurts out answers before questions have been completed
– Has difficulty awaiting turn
– Interrupts or intrudes on others
For the diagnosis of ADHD, the aforementioned symptoms must have been present prior to age 12 with a frequency and severity that exceeds what is expected for the individual’s age, and must negatively affect the child’s performance both at school and at home. In addition, the doctor will also ensure that any of these symptoms are not due to another disorder.