title: Interpreting meta-regression: application to recent controversies in antidepressants' efficacy.
abstract: A recent meta-regression of antidepressant efficacy on baseline depression severity has caused considerable controversy in the popular media. A central source of the controversy is a lack of clarity about the relation of meta-regression parameters to corresponding parameters in models for subject-level data. This paper focuses on a linear regression with continuous outcome and predictor, a case that is often considered less problematic. We frame meta-regression in a general mixture setting that encompasses both finite and infinite mixture models. In many applications of meta-analysis, the goal is to evaluate the efficacy of a treatment from several studies, and authors use meta-regression on grouped data to explain variations in the treatment efficacy by study features. When the study feature is a characteristic that has been averaged over subjects, it is difficult not to interpret the meta-regression results on a subject level, a practice that is still widespread in medical research. Although much of the attention in the literature is on methods of estimating meta-regression model parameters, our results illustrate that estimation methods cannot protect against erroneous interpretations of meta-regression on grouped data. We derive relations between meta-regression parameters and within-study model parameters and show that the conditions under which slopes from these models are equal cannot be verified on the basis of group-level information only. The effects of these model violations cannot be known without subject-level data. We conclude that interpretations of meta-regression results are highly problematic when the predictor is a subject-level characteristic that has been averaged over study subjects.
authors: Department of Child and Adolescent Psychiatry, New York University, New York, NY 10016-6023, USA. eva.petkova@nyu.edu
authors: Eva
authors: E
authors: Petkova
authors: Thaddeus
authors: T
authors: Tarpey
authors: Lei
authors: L
authors: Huang
authors: Liping
authors: L
authors: Deng
mesh_terms: D000928:Antidepressive Agents / Q000627:therapeutic use*; D056808:Biostatistics; D018849:Controlled Clinical Trials as Topic / Q000706:statistics & numerical data; D003863:Depression / Q000188:drug therapy; D006801:Humans; D016014:Linear Models; D015201:Meta-Analysis as Topic; D016896:Treatment Outcome
chemical_list: D000928:Antidepressive Agents
keywords: ecological fallacy; finite mixture; infinite mixtures; mixed-effects models