Variation in ABCB1 has been previously associated with a number of psychiatric phenotypes, including opioid36 and cannabis37 dependence, as well as with treatment outcomes for depression38 and addiction.39 The related rodent gene, Abcb1a, is differentially expressed in three brain regions (accumbens shell, central amygdala and ventral tegmental area) of alcohol-preferring animals compared with non-preferring animals.40, 41 Furthermore, ethanol exposure changes ABCB1 expression. An in vitro study of human intestinal cells found that ethanol exposure increased messenger RNA ABCB1 expression level, and that these increases were maintained even after a week of ethanol withdrawal.42 Similarly, ABCB1 expression was increased in lymphoblastoid cell lines following ethanol exposure,32 and in rodents, Abcb1a expression was increased in the nucleus accumbens of alcohol-preferring rats following alcohol exposure.43
