There are a number of theories of addiction, and most addiction experts believe that addiction is caused by a combination of social and genetic factors (both nature and nurture). The Genetic Theory of addiction is based on the idea that addiction has a basis in our genes. A lot of research has been done on genetics and alcoholism, and the latest research does suggest that alcoholism probably has some genetic components.
Here are a few resources that discuss the Genetic Theory:
The Meaning of Addiction: Theories of Addiction
The Implications and Limitations of Genetic Models of Alcoholism and Other Addictions
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