Attention Deficit Hyperactivity Disorder (ADHD) is diagnosed in children and adolescents by a clinical interview with a child mental health professional who is trained to evaluate and diagnose. Most commonly, these professionals are child and adolescent psychiatrists, psychologists or neurologists. Neuropsychological testing can suggest the diagnosis, but without a clinical assessment, are not enough to make the diagnosis. ADHD cannot yet be diagnosed in an individual child using brain imaging like MRI, PET or CT. Technically, in order to be diagnosed with ADHD, a child must have at least six ADHD symptoms of either inattention, hyperactivity-impulsivity, or both. In addition, these symptoms must be present for at least 6 months or longer, be present before the age of seven, and cause significant impairment or difficulties in two or more settings, such as home, school/work or social settings. The symptoms of inattention include having difficulty maintaining attention, having difficulties listening or following instructions, making careless mistakes, avoiding tasks that require a sustained focus, being forgetful, getting distracted easily and losing things easily. The symptoms of hyperactivity-impulsivity include having difficulty engaging in quiet activities, being restless (such as leaving the classroom), excessively talking or blurting out answers, often interrupting others and having difficulty with waiting their turn.