The green is for left putamen, and, the red is for the right one. We use ‘a’ for the relationship between rs13107325 and putamen, ‘b’ for the relationship between putamen and alcohol consumption, ‘c’ for the relationship between rs13107325 and alcohol consumption, ‘c” for the relationship between rs13107325 and alcohol consumption after excluding the effect of putamen, and ‘ab’ as the mediation effect. The significance tests are based on the bootstrapping method (10,000 times). Z- statistics and the corresponding P values are provided in parentheses. The brain icon was created using Mango software, version 4.1 (http://ric.uthscsa.edu/mango/).