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:
- Combined presentation (ADHD/C) - Requires 5 or more symptoms of both inattention AND hyperactivity-impulsivity for at least 6 months 1
- 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
- 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.