There are three subtypes of ADHD defined in both the Diagnostic and Statistical Manual of Mental Disorders (DSM)-IV and the DSM-5 based on types of symptoms displayed: primarily inattentive, primarily hyperactive/impulsive and combined.13,14
- The primarily inattentive subtype is the second most common and was formerly known as Attention Deficit Disorder (ADD). This subtype demonstrates a more equal distribution between males and females. Some children will be initially diagnosed with this subtype and when symptoms associated with hyperactivity/impulsivity become apparent, the diagnosis may change to the combined subtype. Conversely, when children initially diagnosed with the combined subtype ‘outgrow’ the hyperactivity, the diagnosis may change to this subtype.
- The primarily hyperactive/impulsive subtype frequently describes very young children who may have the combined subtype but have not reached the age where inattention becomes evident.
- In the combined subtype, the patient displays symptoms consistent with both inattention and hyperactivity/impulsivity and typically has the most symptoms. This is the most common subtype and about which the most is known.
- DSM-5 adds a fourth subtype, Inattentive (Restrictive) where the criterion for inattentive are met but no more than 2 symptoms from hyperactive/impulsive have been present for the last 6 months.