Harvard Mental Health Letter

Questions & Answers: Is addiction hereditary?

Q. Is addiction hereditary?

A. There is plenty of evidence for a connection between genetic endowment and addiction to alcohol and drugs. By analyzing patterns of inheritance, researchers have learned that heredity accounts for about half of the risk that a person will develop an addiction. Addiction is a medical illness and develops in the same way as many other illnesses. A person with some underlying genetic vulnerability is exposed to an environment that brings on the illness. In the case of drug and alcohol addiction, common environmental factors are stress and, of course, availability of the addictive substances.

Genes shape temperament: People who are impulsive, take risks, and habitually seek new experiences are more likely to become addicted. Genes also govern responses to stress. The pharmacokinetics of addictive substances — how quickly they are absorbed, broken down, and excreted — is under genetic control, too, as is the pharmacodynamics — the intensity of a person's response to the substance. Heredity can also raise the risk of developing a psychiatric disorder that makes addiction more likely.

We have begun to connect the dots between what genes do and how they influence the brain's susceptibility to addiction. Of greatest interest are the brain's reward system; the amygdala, which reacts to threats; and the prefrontal cortex, which organizes our responses to the environment.

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