A placebo by proxy effect occurs when a patient’s response to therapy, assessed either objectively or subjectively, is affected by the behavior of other people who know that the patient is undergoing therapy. We recruited 58 children aged 2–5 years who reported frequent tantrums and examined the effect of a pharmacologically inert substance (flower essence) that is purported by the manufacturers to reduce temper tantrums. Tantrum frequency, tantrum severity, and parental mood were measured on 5 occasions over 8 days before treatment and on a further 5 occasions over 10 days after the start of treatment. Compared to the period before treatment, there was a continuing reduction in tantrum frequency (p = .002) and severity (p = .003) over the 8 days of placebo treatment. There were significant day-to-day correlations between parents’ mood and tantrum frequency (r = .23) and severity (r = .19). Children’s response to treatment for tantrums is associated with the beliefs and mood of the adult carer. We cannot say whether tantrum reduction was due to objective changes in child behavior, changes in parental perception, or both, but both are clinically important changes.
