This article reviews existing evidence for the use of locomotor activity measures in diagnosing ADHD. The authors conducted a meta-analysis of published studies using motion measures to compare patients with ADHD with controls and then conducted a case control study using the McLean motion activity test (MMAT) on a sample of child, adolescent and adult ADHD patients (N=81) and matched controls (N=91).
The meta-analysis procedure involved searching several electronic medical databases and selecting only articles which used validated methods for diagnosing ADHD, which compared ADHD subjects to healthy controls and which reported data in ways that enabled the authors to calculate the effect sizes as measured by standardized mean differences (SMD) between study groups. A total of 18 studies were chosen, 13 of which involved actigraphy measures and 5 which used motion tracking systems. The combined sample sizes were 570 ADHD patients (305 children and adolescents and 265 adults) and 515 controls (equally divided between youth and adults). The SMD (or effect size) between ADHD subjects and controls was 0.64 using actigraphy measures and 0.92 using the motion tracking systems. The SMD or pooled effect size for youth was 0.75 and for adults was 0.73, indicating that excessive motion is seen as often in adult ADHD patients as in children and adolescents. This contradicts the prevailing view that excessive motor activity is less prominent in adults as compared to youth with ADHD.
The authors then conducted a case control study comparing ADHD patients and controls. Patients were diagnosed using a comprehensive assessment procedure consisting of structured psychiatric interviews, Conners’ rating scales and the BRIEF (a measure of executive functioning). Subjects were administered the MMAT, an infrared motion tracking system that measures the micro-movements of participants during a Go/No-Go task (15 minutes for youth and 20 minutes for adults). ADHD groups differed significantly from controls on most motion measures, with an effect size of 0.83 for adults and 0.45 for children and adolescents. Reaction time variability was also significantly greater in the ADHD sample across all ages (p<0.05). Interestingly, there were no differences in excessive motion seen among the different ADHD subtypes (combined vs inattentive vs hyperactive vs NOS).
The authors conclude that locomotor hyperactivity is a core constituent feature of ADHD even in adults and across all diagnostic subtypes. They further suggest that objective locomotion measures may be useful in improving the process of diagnosing difficult cases of ADHD. While it is still premature to suggest that movement measurement devices like the MMAT are necessary for diagnosing ADHD in most patients, there is certainly a role for using them in clinical practice. Future research will help delineate additional uses for these tools in diagnosing other neurodevelopmental disorders.
Murillo LG, Cortese S, Anderson D, DiMartino A, Castellanos FX (2015). “Locomotor activity measures in the diagnosis of attention deficit hyperactivity disorder: Meta-analyses and new findings.” Journal of Neuroscience Methods Epub ahead of print March 11, 2015. DOI: 10.1016/j.jneumeth.2015.03.001.