Attention Deficit Hyperactivity Disorder - Classification

Classification

ADHD may be seen as one or more continuous traits found normally throughout the general population. It is a developmental disorder in which certain traits such as impulse control lag in development. Using magnetic resonance imaging of the prefrontal cortex, this developmental lag has been estimated to range from 3 to 5 years. However, the definition of ADHD is based on behaviour and it does not imply a neurological disease. ADHD is classified as a disruptive behavior disorder along with oppositional defiant disorder, conduct disorder and antisocial personality disorder.

The Diagnostic and Statistical Manual of Mental Disorders (DSM-IV-TR) classifies ADHD according to the predominance of symptoms of:

1. Inattention;
2. Hyperactivity–impulsivity;
3. or a combination of both (Combined type).

This subdivision is based on presence of at least six out of nine long-term maladaptive symptoms (lasting at least 6 months) of either inattention, hyperactivity–impulsivity, or both. Thus, a child who is diagnosed with the inattention subtype may also show signs of hyperactivity–impulsivity, and vice-versa. To be considered, the symptoms must have appeared before the age of 6, manifest in more than one environment (e.g. at home and at school or work), and not be better explained by another mental disorder.

Most children with ADHD have the combined type. Children with the inattention subtype are less likely to act out or have difficulties getting along with other children. They may sit quietly, but without paying attention to what they are doing. Therefore, the child may be overlooked, and parents and teachers may not notice symptoms of ADHD.