It's well known that family members of alcoholics are more likely to have drinking problems themselves, but new research shows that brain-chemistry characteristics may provide high-risk family members with some protection from addiction.

Science Daily reported Sept. 5 that brain scans of family members of alcoholics found that those who were not problem drinkers themselves had higher levels of dopamine D2 receptors in their brains than nonalcoholics from families with no history of alcoholism. The dopamine system in the brain is intimately involved in addiction to alcohol and other drugs.

"This suggests that dopamine D2 receptors in these brain regions protect high-risk individuals from becoming alcoholic," said researcher Gene-Jack Wang of Brookhaven National Laboratories. "This protective effect may combine with emotional and environmental factors to compensate for higher inherited vulnerability."

The study also found that people with high levels of dopamine D2 receptors tended to be more extroverted and motivated by positive rewards, regardless of family history of alcoholism. Such "positive emotionality" is thought to decrease the probability of individuals developing drinking problems.

Researchers suggested that therapy centered on raising dopamine levels could prevent addiction in other at-risk individuals. Animal studies have shown that genetically manipulating dopamine levels lowered alcohol consumption in rats.

"Higher levels of dopamine D2 receptors may provide protection against alcoholism by triggering the brain circuits involved in inhibiting behavioral responses to the presence of alcohol," said lead study author Nora D. Volkow, director of the National Institute on Drug Abuse.

The study appears in the September 2006 issue of the Archives of General Psychiatry.