 found evidence for an association of the short allele of the 5-HTTLPR (SLC6A4) with AD, but the overall effect size estimated by odd ratios was found weak.As expected in a complex condition like alcohol dependence, the disagreement in the association between AD and 5-HTTLPR likely reflects the impossibility for a single genetic determinant to explain the whole of the risk.Aside from chemical components which may cause a predisposition to alcohol dependence and blackouts, expectations of alcohol use may predispose drinkers toward alcoholism and blackouts.