Genetic studies of alcohol dependence in the context of the addiction cycle Alcohol dependence is heritable. Two factor contribute to alcohol dependence - environmental conditions, and genes. It is estimated that genes contribute to about 50-60% of the phenotype.It is hard to nail down the exact genes because everything is heterogenous. Researchers study twin studies and adoption data to define the genetic components of alcohol dependence. Both twin and adoption studies show high correlation between family members and the participants susception to alcohol dependency. Research then ran an GWAS (genome wide association study) and found multiple genetic variants that contribute to alcoholism.