Dopaminergic Gene Polymorphisms and Personality Traits in Athletes: A Systematic Review and Exploratory Quantitative...

Personality traits relevant to sport performance are partly heritable, and dopaminergic genes have been proposed as contributors to individual differences in athlete personality. However, evidence for these associations remains inconsistent. To systematically review and synthesize evidence on associations between dopaminergic gene polymorphisms and personality traits in athletes. Following PRISMA 2020, STREGA, and SWiM recommendations, databases were systematically searched using predefined eligibility criteria. Fourteen primary association studies met the eligibility criteria; one systematic review was identified and retained as a background source only, contributing no primary data. The protocol was prospectively registered in PROSPERO (CRD420261430605). Study quality was assessed using a STREGA-informed checklist. Standardized mean differences (Hedges' g) were calculated where genotype-specific means and standard deviations were available. Because of overlapping cohorts and heterogeneous reporting, conventional meta-analysis was not feasible; therefore, an exploratory quantitative synthesis, vote counting, and allele/genotype frequency analyses were performed. Most studies involved male Caucasian Polish combat-sport athletes, with two independent cohorts from Egypt and Turkey, and examined DRD2, DRD4, COMT, DAT1/SLC6A3, and ANKK1 polymorphisms. The most frequently examined association was between DRD2 rs1799732 and reward dependence, for which two cohorts reported small, directionally concordant estimates whose confidence intervals both included the null (g = -0.18, 95% CI -0.44 to +0.09; g = -0.20, 95% CI -0.40 to +0.01); because these cohorts share controls and overlapping participants, they were not pooled and do not constitute independent replication. Other associations were generally small and study-specific. The COMT rs4680 Met allele was less frequent in athletes than controls (OR 0.75, 95% CI 0.59-0.96). Evidence was limited by overlapping cohorts, small samples, methodological heterogeneity, and predominant reliance on a single research network; the few studies conducted outside that network reported largely null genotype-personality associations. Current evidence is insufficient to establish associations between dopaminergic polymorphisms and sport-related personality traits: the reported associations are derived almost entirely from a single, non-independent research network, and no gene × trait association has been replicated in an independent sample. Certainty of the cumulative evidence, appraised with the Venice criteria for genetic associations, was weak for every gene × trait association examined. Large, independent, multicenter studies using standardized phenotyping, together with polygenic and epigenetic approaches, are needed before any inference can be drawn.