For the chromosome 4 locus, carrying an African ancestry allele in this region increased the SRE-5 score, indicating a lower response to alcohol during the first five times the individual used alcohol. This might initially appear counterintuitive, because AA typically report faster rates of stimulation in response to alcohol compared to EA (Pedersen & McCarthy, 2013). Recent studies suggested that findings from admixture mapping need not conform to expectations regarding the direction of disease prevalence; i.e., even though a disorder is more common in one ancestral group, admixture mapping may result in identification of variants of protective effect (Molineros et al., 2013; Sofer et al., 2017; Wang et al., 2019). As long as the disease-causing variants have different allele frequencies between different ancestries, these variants will be detected by admixture mapping (Patterson et al., 2004), regardless of their directions of effect on the phenotype. Other variants that cannot be detected in our current analysis might be responsible for the population-specific effect.
