ADHD may be classified according to the DSM V criteria into three subgroups: predominantly inattentive type, predominantly hyperactive-impulsive type, and combined type.^[1]

ADHD may be classified according to the DSM V criteria into three subgroups: predominantly inattentive type, predominantly hyperactive-impulsive type, and combined type. Distinctions are made according to the following criteria:^[1]

1. ADHD Combined Type: ≥6 symptoms of hyperactivity/impulsivity and inattention have been observed for ≥6 months
2. ADHD Predominantly Inattentive Type: ≥6 symptoms of inattention (but <6 symptoms of hyperactivity/impulsivity) have been present for ≥6 months
3. ADHD Predominantly Hyperactive-Impulsive Type: ≥6 symptoms of hyperactivity/impulsivity (but <6 symptoms of inattention) have been present for ≥6 months

For detailed descriptions of the symptoms of hyperactivity/impulsivity and inattention used in the diagnosis of ADHD, refer to the Attention-deficit hyperactivity disorder diagnostic criteria page.

The terminology of ADD expired with the release of the fifth edition of the DSM in 2013. ADHD is the term currently used to describe one distinct disorder which can manifest itself as hyperactivity/impulsivity (ADHD, predominately hyperactive-impulsive type), inattention (ADHD predominately inattentive type), or both (ADHD combined type).

• ADHD is a developmental disorder insofar as patients experience a developmental lag in certain traits, such as impulse control. Using magnetic resonance imaging, this developmental lag has been estimated to range between 3 and 5 years in the prefrontal cortex of those with ADHD patients in comparison to their peers;^[2] consequently, these delayed attributes are considered an impairment.
• ADHD has also been classified as a behavior disorder.
• ADHD has also been classified as a neurological disorder or a combination of classifications such as a neurobehavioral or neurodevelopmental disorder.^[3]
• In the tenth edition of the International Statistical Classification of Diseases and Related Health Problems (ICD-10), the symptoms of ADD are given the name “Hyperkinetic disorders.” When a conduct disorder (as defined by ICD-10^[4]) is present, the condition is referred to as “Hyperkinetic conduct disorder.” Otherwise, the disorder is classified as “Disturbance of Activity and Attention,” “Other Hyperkinetic Disorders,” or “Hyperkinetic Disorders, Unspecified.” The latter is sometimes referred to as, “Hyperkinetic Syndrome.”^[4]