[Executive function characteristic in boys with attention deficit hyperactivity disorder comorbid learning...

Area of Science:

• Neuroscience
• Developmental Psychology
• Clinical Psychology

Background:

• Attention deficit hyperactivity disorder (ADHD) is a neurodevelopmental disorder characterized by persistent patterns of inattention and/or hyperactivity-impulsivity.
• Learning disabilities (LD) are neurodevelopmental disorders that affect specific academic skills, such as reading, writing, or mathematics.
• Executive functions (EF) are a set of cognitive processes that control and regulate other cognitive processes, including planning, working memory, and inhibition.

Purpose of the Study:

• To investigate the executive function (EF) characteristics in boys diagnosed with attention deficit hyperactivity disorder (ADHD).
• To compare the EF profiles of boys with pure ADHD against those with ADHD comorbid with learning disabilities (LD).
• To elucidate the impact of comorbid LD on EF deficits in boys with ADHD.

Main Methods:

• A cohort of 66 boys was recruited, comprising 22 with pure ADHD, 22 with ADHD and LD, and 22 typically developing controls, all diagnosed according to DSM-IV criteria.
• Groups were matched for age (within 6 months) and ADHD subtypes to ensure comparability.
• A comprehensive battery of neuropsychological tests was administered to assess various executive functions, including the Stroop color-word task, Rey complex figure test, digit span test, trail making test, Tower of Hanoi, and verbal fluency test.

Main Results:

• While verbal IQ (VIQ) did not differ significantly across groups, both pure ADHD and ADHD+LD groups exhibited lower performance IQ (PIQ) than controls. ADHD+LD boys also had lower overall IQ scores compared to controls.
• Both ADHD and ADHD+LD groups demonstrated significant impairments in specific EF domains, including processing speed (time for number-letter task) and cognitive flexibility (shifting time), as well as increased repetitive errors in verbal fluency.
• The ADHD+LD group showed more pronounced deficits across a wider range of EF measures, including inhibition (Stroop task interference), working memory (immediate and delayed recall on Rey complex figure test), planning (Tower of Hanoi errors), and sustained attention/processing speed (Trail Making Test time). ADHD+LD boys also made more errors on color naming in the Stroop task compared to pure ADHD boys.

Conclusions:

• The study confirms a strong association between ADHD and executive function deficits, irrespective of the presence of comorbid LD.
• Boys with ADHD and comorbid LD exhibit more significant impairments in executive functions, encompassing inhibition, working memory, set shifting, and fluency, compared to boys with ADHD alone.
• These findings suggest that both ADHD and LD are independently and potentially synergistically associated with executive function deficits, highlighting the complex interplay of these conditions.