Effect of Psychostimulant Medications on Muscle Tone in Adults with Attention Deficit Hyperactivity Disorder: Within-Subject Repeated-Measure Study Design

Abstract

Abstract Background: To determine PF spasticity and the effect of PS on PF spasticity and ankle plantarflexor resistance to stretch (PFRS) in adults with Attention-Deficit/Hyperactivity Disorder (ADHD). Methods: Participants completed two visits (off-medication and on-medication). During both visits, the Modified Ashworth Scale (MAS) was administered to measure PF spasticity. Two device-measured (isokinetic-dynamometer [Biodex] and surface electromyograph [sEMG]) tests assessed PFRS: reflex mediated, and non-reflex mediated. Results: Adults with ADHD (n= 39, 31 females; mean age=28.6±6.7 years). Overall, adults with ADHD displayed elevated PF spasticity (average MAS>1). PS use was not associated with changes in PFRS [F(1,38)=0.001;p=0.972;ηp2=0.01]. A sub-analysis indicated that PS was associated with reduced PFRS [F(2,36)=4.449;p=0.019;η2=0.20], specifically with the reflex-mediated component, among the predominantly inattentive ADHD subtype. Conclusions: Adults with ADHD displayed increased PF spasticity. PS use was associated with reduced reflex mediated PFRS in adults with the predominantly Inattentive subtype of ADHD only.