Hyperactivity persists in male and female adults with ADHD and remains a highly discriminative feature of the disorder: a case-control study

Abstract

Background: Symptoms of hyperactivity are believed to fade with age leaving ADHD adults mostly inattentive and impulsive. Our aim was to test this assertion using objective measures of hyperactivity, impulsivity and inattention.

Method: Participants were 40 subjects with ADHD (23M/17F; 35±10 yrs) and 60 healthy adults (28M/32F; 29±9 yrs) blindly assessed using Wender-Reimherr interview ratings, Structured Clinical Interview for DSM-IV Disorders and DSM-IV criteria. Infrared motion capture systems tracked head and leg movements during performance of a No-4's cognitive control task. Subjects also completed the Conners' CPT-II.

Results: ADHD and controls differed significantly in activity and attention. Effect sizes for activity measures (d' = 0.7-1.6) were, on average, two-fold larger than differences in attention or impulsivity, correlated more strongly with executive function ratings and were more discriminatory (ROC area = 0.83 for activity composite, 0.65 for No-4's distraction composite, 0.63 for Conners' CPT-II confidence index, 0.96 for the combined activity and attention diagnostic index). This finding was true for subjects with the predominantly inattentive subtype as well as subjects with combined or predominantly hyperactive/impulsive subtype. Males and females with ADHD were equally active. The superior accuracy of activity measures was confirmed using Random Forest and predictive modeling techniques.

Conclusions: Objectively measured hyperactivity persists in adults with ADHD and is a more discriminative feature of the disorder than computerized measures of inattention or impulsivity. This finding supports the hypothesis that a deficient ability to sit still remains a defining feature of the disorder in adults when it is measured objectively.

Figure 1

Infrared motion analysis patterns tracing the movement path of markers attached to the head, left and right shins and ankles of four representative subjects in 5-minute blocks over the course of the 20-minute cognitive control task. Subjects included in the figure were males and females from each group whose activity measures were closest to the ADHD and control group means.

Figure 2

Receiver operating characteristic curves for age and gender covaried composite measures of attention and activity. Conners’ Confidence Index comes from the Conners CPT-II. Attention Severity, Activity Severity and Diagnostic Composites derived from the No-4’s cognitive control task and infrared motion analysis.

Figure 3

Random forest regression analysis showing the relative importance of activity and attention measures in classifying subjects as ADHD or controls. Variables are rank ordered by importance, which was determined in two ways. The left panel indicates importance by how much the permutation (effective elimination) of a given variable decreases the accuracy of the overall fit. The right panel indicates importance by how much the permutation of a variable attenuates the ability of the specific nodes in the random forest to accurately split the sample. Variables that are associated with the greatest decrease in accuracy or Gini coefficient following permutation are the most important.