A second novel finding of the current study was the independent and epistatic interactions of DAT1 and OPRM1 genes on recent drinking patterns as reported on the TLFB interview during the 90 days preceding the assessment interview. DAT1 A9 allele was associated with a greater number of drinking days, but this effect was attenuated in OPRM1 *G carriers. The OPRM1 *G allele was independently associated with fewer heavy drinking days, but did not affect average number of drinks per drinking day over the 90-day TLFB period. There were no epistatic effects of DAT1 A9 and OPRM1 *G genotypes on number of heavy drinking days or average number of drinks per drinking day.
