Do larger studies find smaller effects? The example of studies for the prevention of conduct disorder.

European Child & Adolescent Psychiatry
Brid McMahonJonathan Green

Abstract

There is some emerging evidence in medicine that larger clinical trials tend to be associated with smaller effect sizes. Much of the evidence-base currently informing practice in Child Psychiatry relies on relatively small trials. We therefore investigated the relationship between trial size and effect size in research within a key area of child mental health. A recent systematic review of 20 trials of prevention of conduct disorder was subjected to meta-regression, to examine the relationship between study size and effect size, and to explore hypothesised confounding variables. In this sample of studies, reported effect size was inversely related to sample size. This effect is not explained by year of publication, intervention type or quality of methodology in the study. Our finding is consistent with other reports in the literature. The origin of this effect is not yet clear. However if replicated it clearly has significant implications for the way trials in child mental health are interpreted.

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Citations

Dec 7, 2013·Clinical Child and Family Psychology Review·Roberto Maniglio
May 3, 2011·Journal of Clinical Epidemiology·Santiago G MorenoKeith R Abrams
Jun 22, 2015·Cortex; a Journal Devoted to the Study of the Nervous System and Behavior·Angela de Bruin, Sergio Della Sala
Apr 25, 2009·Alcoholism, Clinical and Experimental Research·Alireza ShirpoorMarine Yegiazarian
Jun 8, 2011·Journal of Child Psychology and Psychiatry, and Allied Disciplines·Sally Ozonoff
Sep 11, 2013·Journal of Clinical Epidemiology·Wilco C H JacobsF Cumhur Oner
Feb 11, 2015·The Journal of Evidence-based Dental Practice·Spyridon N PapageorgiouNikolaos Kotsanos
Aug 11, 2020·Nicotine & Tobacco Research : Official Journal of the Society for Research on Nicotine and Tobacco·Jennifer M BettsStephen T Tiffany

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