Associations of the COMT Val158Met polymorphism with working memory and intelligence - A review and meta-analysis

The Val158Met polymorphism influences the activity of the Catechol-O-Methyl-Transferase (COMT), an enzyme involved in dopamine metabolism. Dopamine availability is vital for prefrontal functions. Therefore researchers claimed that Val158Met is causal for cognitive abilities. Published findings from single studies report mixed results. This meta-analysis examines the COMT genotype associations with working memory and intelligence in healthy populations. A systematic literature search was conducted yielding 412 studies, 58 of which could be included in the meta-analyses. There were no substantial COMT Val158Met effects on cognitive abilities, showing that either the true effect is zero or too small to be uncovered due to insufficient power of the analysis. The discussion focuses on power issues in research synthesis in general and their implications concerning the relation of Val158Met with working memory and intelligence in specific. Desiderata for research synthesis closely resemble those formulated in the open science framework: fully transparent single study design and data use of scientifically recommended methodologies.