AD(H)D is a neurodevelopmental disorder that is characterised by features of both a mental health condition and a specific learning difficulty. 
As noted in the fifth edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5), AD(H)D is characterized by:
  • a persistent pattern of inattention and/or hyperactivity-impulsivity that interferes with normal functioning or development
  • is present in multiple settings (e.g. home, school, work)
  • symptoms interfere with or reduce the quality of social, academic or occupational functioning. 
Hyperactive-impulsive symptoms are less common in adults, who may present predominantly with problems of inattention.