What is the most common type of Attention Deficit Hyperactivity Disorder (ADHD)?

The Most Common Type of ADHD

The combined type of ADHD is the most common presentation, characterized by both inattentive and hyperactive-impulsive symptoms. 1

ADHD Types and Their Prevalence

According to the DSM-5 criteria, ADHD is categorized into three main presentations:

1. Combined presentation (ADHD/C) - Requires 5 or more symptoms of both inattention AND hyperactivity-impulsivity for at least 6 months 1
2. Predominantly inattentive presentation (ADHD/I) - Requires 5 or more symptoms of inattention but fewer than 5 symptoms of hyperactivity-impulsivity for at least 6 months 1
3. Predominantly hyperactive-impulsive presentation (ADHD/HI) - Requires 5 or more symptoms of hyperactivity-impulsivity but fewer than 5 symptoms of inattention for at least 6 months 1

The combined type is consistently identified as the most common presentation across multiple guidelines and research studies, with the inattentive type being the second most common, and the hyperactive-impulsive type being the least common.

Key Characteristics of Each ADHD Type

Combined Type (Most Common)

• Features both inattentive and hyperactive-impulsive symptoms
• Often presents with more severe functional impairment
• Higher rates of comorbid conditions, particularly substance use disorders 2
• Typically more easily recognized due to the presence of both symptom clusters

Predominantly Inattentive Type

• Characterized by poor attention to detail, difficulty sustaining attention, and organizational challenges
• May be less disruptive but still significantly impaired
• More associated with internalizing problems 3
• Often presents with lower attention and vigilance on neuropsychological testing 3
• May be underdiagnosed, especially in girls and adults, due to less obvious symptoms

Predominantly Hyperactive-Impulsive Type

• Characterized by fidgeting, excessive talking, and difficulty waiting turn
• More common in younger children
• Often evolves into combined type as children age
• Associated with faster response speed but deficits in cognitive control 3

Clinical Implications

The predominance of the combined type has important clinical implications:

• Clinicians should be vigilant in assessing for both symptom clusters, as they frequently co-occur
• Treatment approaches may need to address both inattention and hyperactivity/impulsivity
• Higher risk of comorbidities in combined type may necessitate more comprehensive treatment planning

Diagnostic Considerations

When evaluating for ADHD, clinicians should:

• Use standardized rating scales based on DSM-5 criteria
• Collect information from multiple sources (parents, teachers, self-reports)
• Document functional impairment across settings
• Screen for common comorbidities, which vary by subtype 1, 4

Age-Related Variations

• In children, the combined type is most prevalent, with hyperactive symptoms often more obvious
• In adolescents and adults, hyperactive symptoms may become less apparent, but inattentive symptoms often persist 4
• Some patients initially diagnosed with predominantly inattentive type may have previously had hyperactive symptoms that diminished with age 2

The recognition of combined type as the most common presentation helps guide appropriate assessment and treatment planning for individuals with ADHD across the lifespan.