Genetic testing already has important clinical applications in the prevention of diseases. Screening for deleterious variants in BRCA1/2 associated with increased risk of hereditary breast and ovarian cancer in women is becoming more common, and individuals with deleterious variants of BRCA1/2 can increase surveillance (such as increasing frequency of mammograms), undergo prophylactic surgery and take steps to reduce other risk factors. However, implementation of genetic testing in prevention programs for drug addiction has additional complexity as experimentation and initiation of drug use is more or less a choice made by the individual. It is unclear whether targeted prevention programs for individuals, in particular youths and adolescents who are the prime targets of such interventions, based on certain genetic vulnerabilities to developing drug dependence will be effective or socially acceptable. While we are still far from having sufficiently powerful genetic predictors for addictions, one example of genetic prevention that could be useful today is the Glu487Lys variant of aldehyde dehydrogenase-2 (ALDH2), which is found in approximately 500 million people as described above. Physicians should inform patients with the loss-of-function variant of their elevated risk of upper GI cancer and suggest they refrain from consuming large amounts of alcohol (42).
