Placebo response and its determinants in children with ADHD across multiple observers and settings: A randomized clinical trial

Int J Methods Psychiatr Res. 2018 Mar;27(1):e1572. doi: 10.1002/mpr.1572. Epub 2017 Jun 30.


This study aims to quantify placebo response (PR) in children with attention deficit hyperactivity disorder (ADHD) as assessed by parents and teachers and to explore some of its determinants. Five hundred and forty children with ADHD (ages 6-12) were recruited to a randomized, double-blind, placebo-controlled crossover trial with methylphenidate. The main outcome variable was Conners' Global Index (CGI), based on assessment of behaviour by parents (CGI-P) and teacher (CGI-T). PR was calculated as the difference between CGI-P/T scores at baseline and placebo week. There was a highly significant PR as assessed by the parents' and teachers' (p < 0.001). The magnitude of PR as assessed by parents was greater (10.57 points) compared to that assessed by teachers (3.93 points). The determinants of PR were different between parents and teachers. For parents, income, marital status, education, maternal smoking during pregnancy, and prior psychostimulant exposure (PPE) showed a significant effect on PR. For teachers, only ethnicity and PPE had an effect. The pattern of PR revealed two distinct profiles that may shed some light on the mechanisms involved in PR. PR in children with ADHD varies depending on the setting of the observations and the evaluator. Several psychosocial factors have been identified as modulators of PR. This is relevant for the design and interpretation of clinical trials and for clinical practice.

Trial registration: NCT00483106.

Keywords: ADHD; parents; placebo response; predictors; teachers.

Publication types

  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Attention Deficit Disorder with Hyperactivity / drug therapy*
  • Central Nervous System Stimulants / pharmacology*
  • Child
  • Cross-Over Studies
  • Double-Blind Method
  • Female
  • Humans
  • Male
  • Methylphenidate / pharmacology*
  • Outcome Assessment, Health Care*
  • Parents
  • Placebo Effect*
  • School Teachers


  • Central Nervous System Stimulants
  • Methylphenidate

Associated data


Grant support