Types of add/adhd
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Types of ADD/ADHD: A Comprehensive Overview
Introduction to ADD/ADHD Subtypes
Attention-Deficit/Hyperactivity Disorder (ADHD) is a complex neurodevelopmental disorder characterized by symptoms of inattention, hyperactivity, and impulsivity. The Diagnostic and Statistical Manual of Mental Disorders (DSM) has evolved over time to better categorize and understand the different manifestations of ADHD. The current DSM-IV criteria identify three primary subtypes: Predominantly Inattentive Type (ADHD-I), Predominantly Hyperactive-Impulsive Type (ADHD-H), and Combined Type (ADHD-C).
Predominantly Inattentive Type (ADHD-I)
Characteristics and Cognitive Profile
The Predominantly Inattentive Type, often referred to as ADD (Attention-Deficit Disorder), is characterized by significant inattention without the hyperactive and impulsive behaviors seen in other subtypes. Research suggests that individuals with ADHD-I may struggle primarily with working memory and processing speed, rather than response inhibition . These individuals often exhibit symptoms such as forgetfulness, difficulty sustaining attention, and a tendency to be easily bored rather than distractible.
Neurobiological Differences
Neurobiological studies indicate that ADHD-I may involve different brain regions compared to other ADHD subtypes. Specifically, disturbances in the frontal-parietal loop, rather than the frontal-striatal loop, are implicated in ADHD-I. This suggests that ADHD-I and ADHD-C may be distinct disorders with different underlying neurobiologies.
Predominantly Hyperactive-Impulsive Type (ADHD-H)
Characteristics and Behavioral Profile
The Predominantly Hyperactive-Impulsive Type is less common and is characterized by hyperactivity and impulsivity without significant inattention. Symptoms include excessive fidgeting, difficulty remaining seated, and impulsive decision-making. However, evidence for the validity of ADHD-H as a distinct subtype is weak, particularly after the first grade, and it is often considered an earlier or milder stage of ADHD-C.
Combined Type (ADHD-C)
Characteristics and Comorbidities
The Combined Type includes both inattention and hyperactivity-impulsivity symptoms. This subtype is the most studied and is associated with a broader range of externalizing behaviors, such as aggression and delinquency, as well as higher rates of comorbid conditions like oppositional defiant disorder and conduct disorder. Children with ADHD-C often exhibit more severe impairments in social, academic, and occupational functioning compared to those with ADHD-I.
Neurobiological and Cognitive Differences
ADHD-C is linked to disturbances in the frontal-striatal loop, which affects response inhibition and executive functioning. This subtype shows greater deficits in response inhibition tasks, such as the antisaccade task, compared to ADHD-I.
Sluggish Cognitive Tempo (SCT) and Its Relation to ADHD
Characteristics and Distinction from ADHD
Sluggish Cognitive Tempo (SCT) is a proposed subtype characterized by symptoms such as daydreaming, mental fogginess, and slow processing speed. SCT is often associated with ADHD-I but is considered by some researchers to be a distinct condition. Individuals with SCT exhibit slower cognitive interference control and output speed, which differentiates them from those with ADHD-C and non-ADHD controls.
Conclusion
The classification of ADHD into distinct subtypes—Predominantly Inattentive Type (ADHD-I), Predominantly Hyperactive-Impulsive Type (ADHD-H), and Combined Type (ADHD-C)—helps in understanding the diverse presentations and underlying mechanisms of the disorder. While ADHD-I and ADHD-C show significant differences in cognitive and neurobiological profiles, the validity of ADHD-H as a distinct subtype remains questionable. Additionally, the concept of Sluggish Cognitive Tempo (SCT) adds another layer of complexity, highlighting the need for further research to refine these classifications and improve diagnostic accuracy and treatment strategies.
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