Objective: We compared the placebo response (PR) as measured by the Test of Variables of Attention (TOVA) and the Conners' Adult ADHD Rating Scale (CAARS) scores. Method: A retrospective data analysis from a double-blind placebo-controlled study of metadoxine-ER in adults with ADHD. An additional database was used for comparison to TOVA response after methylphenidate challenge (TOVA-MPH-R). Results: PR was highest when calculated from the TOVA-Attention Composite Score (ACS). The PR showed significantly fewer variables improving concomitantly compared with MPH-R. The most prominent correlation between the CAARS-PR and the TOVA-PR was in the Omissions score (p = .032), which was age-dependent (b = .0007, p <.001). Discussion: TOVA-PR has an index-specific profile compared with CAARS-PR and TOVA-MPH-R. The partial correlation of TOVA-PR with CAARS-PR suggests that a composite score of TOVA specific indices and CAARS could have a synergic impact to improve the reliability of the response assessment in adult ADHD.
Keywords: adult ADHD; continuous performance test; placebo response.