care [78]. The S allele has also been associated with increased drinking and drug use in US college students who had experienced multiple past year SLEs [79]. Sex-specific effects also have been detected in rhesus macaque monkeys, but in contrast to the Mannheim study, only S allele carrier females with exposure to early-life stress (peer rearing vs maternal rearing) consumed more alcohol and progressively increased levels of consumption over time compared with non–S allele carriers [80]. Finally, COGA (the Collaborative Study on the Genetics of Alcoholism) found no evidence for any interactive effect between 5-HTTLPR genotype and past year SLEs on AD risk [81]. Therefore, G×E results for 5-HTTLPR have thus far been mixed, but this may not be surprising because there is considerable variability in the different studies of both stressors and alcohol-related phenotypes.
