Attention deficit disorder and specific reading disability: separate but often overlapping disorders.

Area of Science:

• Child Psychology
• Neurodevelopmental Disorders
• Behavioral Science

Background:

• Attention Deficit Disorder (ADD) presents heterogeneously in clinic-referred children.
• Previous research indicates varying behavioral presentations and co-occurring conditions within ADD populations.
• Understanding subgroups is crucial for targeted interventions and treatment efficacy.

Purpose of the Study:

• To identify distinct behavioral subgroups within a heterogeneous sample of children diagnosed with ADD.
• To examine the relationship between behavioral subgroups, reading disability (RD), and cognitive/behavioral measures.
• To assess the efficacy of methylphenidate treatment across identified subgroups and RD status.

Main Methods:

• Cluster analysis of teacher ratings to identify behavioral subgroups in 182 children with DSM-III diagnosed ADD.
• Assessment of reading disability (RD) using discrepancy criteria.
• Evaluation of convergent and divergent validity measures, including IQ, achievement scores, and laboratory tasks.
• Analysis of methylphenidate treatment response across subgroups.

Main Results:

• Three behavioral subgroups were identified: ADD with hyperactivity (ADDH), ADD with hyperactivity and aggressivity (ADDHA), and ADD without hyperactivity or aggressivity.
• A significant proportion of the sample had a reading disability (RD), with a higher prevalence in boys.
• Behavioral subgroups differed on externalizing behaviors but not on IQ or achievement scores.
• Methylphenidate demonstrated equal efficacy across all subgroups, irrespective of RD status or dosage.

Conclusions:

• Behavioral heterogeneity in ADD can be categorized into distinct subgroups.
• Reading disability is a common co-occurring condition in ADD, particularly in boys.
• Methylphenidate treatment appears broadly effective for children with ADD, regardless of specific behavioral subtypes or reading impairments.