Snippet from https://www.cdc.gov/ncbddd/adhd/diagnosis.html (emphasis mine):
DSM-5 Criteria for ADHD
People with ADHD show a persistent pattern of inattention and/or
hyperactivity–impulsivity that interferes with functioning or
Inattention: Six or more symptoms of inattention for children up to age 16, or five or more for adolescents 17 and older and adults;
symptoms of inattention have been present for at least 6 months, and
they are inappropriate for developmental level:
Often fails to give close attention to details or makes careless mistakes in schoolwork, at work, or with other activities.
Often has trouble holding attention on tasks or play activities.
Often does not seem to listen when spoken to directly.
Often does not follow through on instructions and fails to finish schoolwork, chores, or duties in the workplace (e.g., loses
Often has trouble organizing tasks and activities.
Often avoids, dislikes, or is reluctant to do tasks that require mental effort over a long period of time (such as schoolwork
Often loses things necessary for tasks and activities (e.g. school materials, pencils, books, tools, wallets, keys, paperwork,
eyeglasses, mobile telephones).
Is often easily distracted
Is often forgetful in daily activities.
Hyperactivity and Impulsivity: Six or more symptoms of hyperactivity-impulsivity for children up to age 16, or five or more
for adolescents 17 and older and adults; symptoms of
hyperactivity-impulsivity have been present for at least 6 months to
an extent that is disruptive and inappropriate for the person’s
Often fidgets with or taps hands or feet, or squirms in seat.
Often leaves seat in situations when remaining seated is expected.
Often runs about or climbs in situations where it is not appropriate (adolescents or adults may be limited to feeling
Often unable to play or take part in leisure activities quietly.
Is often “on the go” acting as if “driven by a motor”.
Often talks excessively.
Often blurts out an answer before a question has been completed.
Often has trouble waiting his/her turn.
Often interrupts or intrudes on others (e.g., butts into conversations or games)
In addition, the following conditions must be met:
Several inattentive or hyperactive-impulsive symptoms were present before age 12 years.
Several symptoms are present in two or more setting, (such as at home, school or work; with friends or relatives; in other activities).
There is clear evidence that the symptoms interfere with, or reduce the quality of, social, school, or work functioning.
The symptoms are not better explained by another mental disorder (such as a mood disorder, anxiety disorder, dissociative disorder, or
a personality disorder). The symptoms do not happen only during the
course of schizophrenia or another psychotic disorder.
The extent and degree of the symptoms matters. For example, some people can have ADHD traits, but an individual with a legitimate psychopathology may have a lifestyle that significantly suffers without treatment. Certain brain volumes are also smaller in ADHD subjects, see
Early results with structural MRI show thinning of the cerebral
cortex in ADHD subjects compared with age-matched controls in
prefrontal cortex and posterior parietal cortex, areas involved in
working memory and attention.
Malenka RC, Nestler EJ, Hyman SE (2009). "Chapters 10 and 13". In Sydor A, Brown RY (eds.). Molecular Neuropharmacology: A Foundation for Clinical Neuroscience (2nd ed.). New York: McGraw-Hill Medical. pp. 266, 315, 318–323. ISBN 978-0-07-148127-4.