AN EXAGGERATED CARDIOVASCULAR-RESPONSE TO METHYLPHENIDATE IN ADHD CHILDREN WITH ANXIETY

The cardiovascular responses to methylphenidate (MPH) were investigate d in anxious and nonanxious children with attention-deficit hyperactiv ity disorder (ADHD). A randomized, double-blind, placebo-controlled cr ossover design was used to evaluate the acute effects of three doses ( 0.3, 0.6, and 0.9 mg/kg) of MPH on cardiovascular function in 63 child ren (34 nonanxious, 29 anxious), aged 6 to 12 years, with ADHD. Restin g heart rate as well as systolic and diastolic blood pressure readings were taken prior to 1 hr after, and 2 hrs after administration of med ication. Results indicated that baseline cardiovascular measures were similar for the two diagnostic groups. MPH produced the expected dose- dependent and time-dependent increases in heart rate and both systolic and diastolic blood pressure in all children. However, MPH produced s ignificantly greater increases in diastolic blood pressure in the anxi ous ADHD group, particularly 1 hr after its administration, than in th e nonanxious ADHD children. Although these stimulant-induced changes w ere generally of little clinical concern, the exaggerated response of the ADHD/ANX children to MPH challenge supports the hypothesis of incr eased sensitivity to augmented noradrenergic function in this group. T he presence of high levels of trait anxiety in some ADHD children alte rs the cardiovascular response to MPH, suggesting that highly anxious children with ADHD may constitute a distinct subgroup of children with ADHD. In this study, anxiety was defined by the child's self-report, so the findings attest to the importance of obtaining children's self- report of internalizing symptomatology. The presence of self-reported anxiety in ADHD children should alert clinicians to the possibility of a differential response to psychostimulants in anxious ADHD children.