Different types of adhd
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Different Types of ADHD: A Comprehensive Overview
Introduction to ADHD Subtypes
Attention-Deficit/Hyperactivity Disorder (ADHD) is a neurodevelopmental disorder characterized by symptoms of inattention, hyperactivity, and impulsivity. The Diagnostic and Statistical Manual of Mental Disorders, 4th Edition (DSM-IV) categorizes ADHD into three primary subtypes: predominantly inattentive type (ADHD-I), predominantly hyperactive-impulsive type (ADHD-H), and combined type (ADHD-C)1.
Predominantly Inattentive Type (ADHD-I)
Clinical Characteristics and Prevalence
ADHD-I is characterized by significant inattention without the hyperactive and impulsive behaviors seen in other subtypes. Children with ADHD-I are often older, more likely to be female, and frequently have comorbid internalizing disorders and learning disabilities2. This subtype is also associated with speech and language problems, and these children are less likely to be treated with stimulants compared to other subtypes2.
Cognitive and Behavioral Profiles
Research indicates that ADHD-I patients exhibit milder clinical symptoms but more severe cognitive impairments compared to ADHD-C patients3. The primary cognitive issue in ADHD-I is often related to working memory rather than response inhibition, which is more typical in ADHD-C4. This subtype is also associated with a primary disturbance in the cortex, particularly in the frontal-parietal loop4.
Predominantly Hyperactive-Impulsive Type (ADHD-H)
Clinical Characteristics and Prevalence
ADHD-H is less commonly diagnosed, especially after the first grade, and there is minimal support for its distinction from other subtypes in terms of etiological influences and treatment response1. This subtype is characterized by hyperactivity and impulsivity without significant inattention.
Cognitive and Behavioral Profiles
Children with ADHD-H are often the least impaired overall but show significant social impairments5. This subtype is more frequently observed in boys and is associated with higher levels of externalizing behaviors7.
Combined Type (ADHD-C)
Clinical Characteristics and Prevalence
ADHD-C is the most common subtype, characterized by a combination of inattention, hyperactivity, and impulsivity. It is more prevalent in males and is associated with higher severity of symptoms and lower quality of life8.
Cognitive and Behavioral Profiles
ADHD-C patients exhibit significant impairments in both cognitive and behavioral domains. They show decreased subcortical volume and specific brain structure changes compared to typically developing individuals3. This subtype is also associated with a primary disturbance in the striatum, particularly in the frontal-striatal loop4.
Distinct and Unrelated Disorders?
Some researchers argue that ADHD-I and ADHD-C may be distinct and unrelated disorders due to significant differences in essential features, demographics, cognitive functioning, family history, treatment response, and prognosis9. This perspective is supported by findings of different underlying neurobiologies and clinical profiles between the subtypes4 9.
Conclusion
ADHD is a heterogeneous disorder with distinct subtypes that exhibit unique clinical, cognitive, and behavioral profiles. While the DSM-IV subtypes provide a useful framework for understanding the disorder, there is growing evidence that ADHD-I and ADHD-C may be distinct disorders with different underlying mechanisms. Further research is needed to refine these classifications and improve diagnostic and treatment approaches.
Sources and full results
Most relevant research papers on this topic
Validity of DSM-IV attention deficit/hyperactivity disorder symptom dimensions and subtypes.
The DSM-IV ADHD subtypes provide a convenient clinical shorthand for describing current levels of inattention and hyperactivity-impulsivity symptoms, but lack sufficient long-term stability to justify classification of distinct forms of the disorder.
Meta-Analysis
Highly CitedA chart review study of the Inattentive and Combined Types of ADHD
ADHD-IA subtype is older, more likely to be female, and has more comorbidities and learning disabilities, but less overall impairment than ADHD-Combined Type, and responds to medical treatment with improved attention and residual hyperactive/impulsive symptoms.
Highly CitedStructural Brain Changes and Associated Symptoms of ADHD Subtypes in Children.
ADHD-Inattentive patients show milder clinical symptoms but more serious cognitive injury than ADHD-Combined patients, with significant differences in clinical symptoms and gray matter damage.
Observational Study
Very Rigorous JournalAttention-deficit disorder (attention-deficit/ hyperactivity disorder without hyperactivity): A neurobiologically and behaviorally distinct disorder from attention-deficit/hyperactivity disorder (with hyperactivity)
The core problem in the truly inattentive type of ADHD is in working memory, with motivation being more of a problem than inhibitory control, and the primary disturbance in the cortex.
Highly CitedComparison of ADHD symptom subtypes as source-specific syndromes.
ADHD subtypes show different patterns of impairment socially and cognitively, with combined (C) and inattentive (I) being the most and least impaired overall, respectively.
Observational StudyHighly CitedBehavioral and cognitive subtypes of ADHD.
ADHD can be divided into behavioral and cognitive subtypes, with behavioral subtypes characterized by inattention, impulsivity, and hyperactivity, and cognitive subtypes exhibiting information processing deficits similar to reading disabilities.
Highly CitedEpidemiology of attention-deficit/hyperactivity disorder (ADHD) in children and adolescents in Africa: a systematic review and meta-analysis
ADHD prevalence in children and adolescents in Africa is 7.47%, with a higher prevalence in boys than in girls, and predominantly inattentive type (ADHD-I) being the most common subtype in both sexes.
Meta-Analysis
Rigorous JournalHighly CitedADHD in adults: clinical subtypes and associated characteristics.
Adult ADHD subtypes differ in severity, life quality, and comorbidities, with the hyperactive/impulsive subtype showing worse quality of life and more frequent anxiety disorders.
Observational StudyADHD Combined Type and ADHD Predominantly Inattentive Type Are Distinct and Unrelated Disorders
ADHD/ combined type and ADHD/predominantly inattentive type are distinct and unrelated disorders, with significant differences in essential features, demographics, cognitive functioning, family history, treatment response, and prognosis.
Literature ReviewHighly CitedDoes actigraphy differentiate ADHD subtypes?
Actigraphy does not differentiate ADHD subtypes, contradicting the DSM-IV's specification that children with ADHD combined type should be more hyperactive than those with predominantly inattentive type.
Observational Study