Intraindividual Variability in Attention-Deficit/Hyperactivity Disorder: An Ex-Gaussian Approach

Area of Science:

• Neuroscience
• Child Psychology
• Developmental Disorders

Background:

• Children with attention-deficit/hyperactivity disorder (ADHD) often exhibit higher intraindividual variability (IIV) in response times.
• Objective measures are needed to complement subjective parent ratings in ADHD diagnosis.

Purpose of the Study:

• To investigate if ex-Gaussian estimates of IIV can differentiate between children with and without ADHD.
• To assess the predictive value of IIV for inattention and hyperactivity/impulsivity symptoms.

Main Methods:

• A computerized go/no-go task was used to estimate trial-by-trial IIV in children aged 6-13.
• A continuous performance test (CPT) assessed inattention and hyperactivity/impulsivity.
• Parent questionnaires provided behavioral ratings.

Main Results:

• Children with ADHD showed significantly greater IIV, commission errors, and parent-rated attention problems.
• IIV predicted omission errors and parent ratings of inattention and hyperactivity/impulsivity.
• IIV predicted group membership (ADHD vs. Control), unlike omission errors.

Conclusions:

• Ex-Gaussian estimated IIV is a promising objective measure for attention problems, outperforming omission errors on CPT tasks.
• While parent ratings remain the primary diagnostic tool for ADHD, IIV can aid in identifying cases needing further evaluation.