Alterations in Pain Response are Partially Reversed by Methylphenidate (Ritalin) in Adults with Attention Deficit Hyperactivity Disorder (<scp>ADHD</scp>)

<jats:title>Abstract</jats:title><jats:sec><jats:title>Background</jats:title><jats:p>Attention deficit hyperactivity disorder (<jats:styled-content style="fixed-case">ADHD</jats:styled-content>) is characterized by dysregulation of sensory processing and neurobiology of dopamine. Although cumulative evidence suggests that dopamine is involved in pain processing, pain perception in <jats:styled-content style="fixed-case">ADHD</jats:styled-content> subjects and the effect of dopamine agonists such as methylphenidate (<jats:styled-content style="fixed-case">MP</jats:styled-content>, Ritalin) on it have rarely been studied.</jats:p></jats:sec><jats:sec><jats:title>Aims</jats:title><jats:p>The aims of this study were to (1) psychophysically assess sensitivity to pain in <jats:styled-content style="fixed-case">ADHD</jats:styled-content> subjects as compared to controls and (2) examine the effects of <jats:styled-content style="fixed-case">MP</jats:styled-content> on pain response in <jats:styled-content style="fixed-case">ADHD</jats:styled-content> subjects.</jats:p></jats:sec><jats:sec><jats:title>Methods</jats:title><jats:p>Thirty subjects with <jats:styled-content style="fixed-case">ADHD</jats:styled-content> and 30 age‐ and gender‐matched controls participated in a preliminary trial. Pain threshold, intensity, and tolerance in response to cold pain stimulation were measured for both groups (<jats:styled-content style="fixed-case">ADHD</jats:styled-content> with no treatment). In addition, the <jats:styled-content style="fixed-case">ADHD</jats:styled-content> group was reassessed following a single dose of <jats:styled-content style="fixed-case">MP</jats:styled-content> treatment.</jats:p></jats:sec><jats:sec><jats:title>Results</jats:title><jats:p>The <jats:styled-content style="fixed-case">ADHD</jats:styled-content> subjects “without <jats:styled-content style="fixed-case">MP</jats:styled-content>” in comparison with controls displayed significantly shorter cold pain threshold (2.8 ± 2.1 vs. 5.8 ± 2.5 seconds, respectively, <jats:italic>P</jats:italic> < 0.001) and cold tolerance (21.8 ± 22.3 vs. 62.8 ± 59.8 seconds, respectively <jats:italic>P</jats:italic> < 0.001). No differences in pain intensities between the groups were found. Following <jats:styled-content style="fixed-case">MP</jats:styled-content> treatment, both cold threshold and tolerance in the <jats:styled-content style="fixed-case">ADHD</jats:styled-content> subjects increased significantly compared to those with no treatment (3.6 ± 2.5 seconds, <jats:italic>P</jats:italic> = 0.011, and 46.4 ± 53.3 seconds, <jats:italic>P</jats:italic> < 0.001, respectively).</jats:p></jats:sec><jats:sec><jats:title>Conclusions</jats:title><jats:p>These results suggest that adults with <jats:styled-content style="fixed-case">ADHD</jats:styled-content> are more sensitive to pain compared with controls and that <jats:styled-content style="fixed-case">MP</jats:styled-content> may exert antinociceptive properties in these subjects. Randomized, controlled trials are warranted to verify these findings.</jats:p></jats:sec>