ABSTRACT
Epidemiological studies have clarified the respective contributions of genetic and environmental components in addiction. A familial aggregation for addiction is widely reported: that is, a tendency to observe the pathology most frequently in relatives of sick patients than in healthy subjects. Two complementary approaches can be implemented to identify genetic factors in addiction. The first strategy, appropriate for when one has no information about the biological origin of the disorder, is called “reverse genetics”. The second strategy is called the “candidate gene” study or the “classic genetics” study. The addictive substances trigger pleasure, or may be used to relieve distress. The important development of the human genetic tools coupled with the creation of national and international consortia to recruit large samples of dependent patients and controls have been successfully used in the genetics on addiction. Epigenetics is the study of gene expression modifications, in response to environmental factors or individual history but in absence of modifications of the DNA sequence.
