This is similar to a number of other common
disorders such as type II diabetes, hypertension, and
bipolar disorder. For each of these disorders, there is no
single gene that leads to the disease. Rather, different
combinations of many genes, most with very small individual
effect, contribute to disease risk. Similarly, different
environmental factors, including social factors, also
contribute to disease susceptibility. Therefore, it is the
complex interplay of genetic and environmental factors
that likely affect the risk of alcohol dependence.