What is the rarest type of ADHD?

Attention-Deficit/Hyperactivity Disorder (ADHD) is a condition known for symptoms like inattention, hyperactivity, and impulsivity. However, not all people with ADHD experience these symptoms in the same way. ADHD is divided into subtypes, and among them, the hyperactive-impulsive type (HT) has been identified as the rarest. This subtype is unique because it involves mainly hyperactivity and impulsivity, without significant inattention.

To understand the rarity of the hyperactive subtype, we can look at a study on Australian children. This study showed that Inattentive ADHD was the most common subtype among children aged 6 to 17. In contrast, the Hyperactive-Impulsive subtype and the Combined type (which involves both inattention and hyperactivity-impulsivity) were less common.

One of the most intriguing aspects of the hyperactive subtype is its instability over time. Research indicates that a significant percentage of children diagnosed with ADHD experience a shift in their subtype as they grow older. This is particularly true for the Hyperactive-Impulsive type, which has the highest rate of subtype shift. This finding implies that children initially diagnosed with this subtype often develop different symptoms or see a change in their diagnosis over time.

The hyperactive subtype also has the highest recovery rates for ADHD. One study found that the majority of children diagnosed with hyperactive ADHD no longer met the criteria for ADHD during at least one follow-up visit:

The Hyperactive-Impulsive subtype was included in the DSM-IV to acknowledge children who primarily exhibit hyperactivity and impulsivity, without significant inattention. This subtype is especially observed in younger children. It's thought to be an early indicator of ADHD, which may evolve into the combined type with age. Recognizing this subtype is crucial for early identification and timely support for children.

A study involving 128 boys with ADHD found that symptoms of hyperactivity and impulsivity are more likely to improve over time compared to difficulties with attention. This research suggests that the hyperactive-impulsive symptoms, characteristic of the Hyperactive-Impulsive subtype, may diminish as children grow older.

When examining ADHD in adults, the hyperactive/impulsive only subtype is very rare. In fact, only 7% of adults with ADHD fall into this category. The majority have the combined subtype or are inattentive only. This further highlights the unique and rare nature of the hyperactive-impulsive subtype of ADHD.

In conclusion, the hyperactive subtype of ADHD, characterized by symptoms of hyperactivity and impulsivity without significant inattention, is the rarest form of ADHD. Its prevalence is particularly low in adults, and it tends to change over time, often evolving into other types of ADHD or improving altogether. This subtype is crucial for early identification and intervention in children, ensuring they receive the necessary support and understanding.