Association between serotonin Cumulative Genetic Score and the Behavioral Approach System (BAS): Moderation by early life environment

•We examined whether serotonergic polymorphisms and early adversity predict BAS.•A Cumulative Genetic Score aggregated the contribution of three polymorphisms.•More serotonergic risk alleles interacted with early adversity to predict lower BAS.•Serotonergic genetic variation and early adversity contribute to reward sensitivity.

The present study investigates if genetic variation in the serotonergic system interacts with early adversity to predict changes in the Behavioral Approach System (BAS), a system that taps into reward processing. In a sample of community adults (N = 236) the influence of single serotonergic candidate polymorphisms on BAS was analyzed, we also examined the aggregate contribution of these genetic variants by creating a Cumulative Genetic Score (CGS). A CGS quantifies an individual’s cumulative risk by aggregating the number of risk alleles across the candidate polymorphisms. After individual gene analysis, three candidate genes rs7305115 (TPH2), rs6311 (HTR2A), and rs6295 (HTR1A) were combined into the CGS. There were no significant interactions between individual candidate polymorphisms and childhood adversity, but the CGS interacted with childhood adversity to explain a significant amount of variance (11.6%) in the BAS. Findings suggest that genetic variations in the serotonergic system in combination with childhood adversity contribute to individual differences in reward sensitivity.