Nora Volkow

"High levels of dopamine receptors seem to make us more sensitive to natural reinforcers," such as our codes of moral, social or personal behavior, says Volkow. That means it's easier for us to balance our desire for pleasure with our desire to achieve social closeness, career success or other positive life goals. Low levels throw off that balance. And some substances, including many illegal drugs, actually change the brain over time by strengthening some connections and weakening others, until taking drugs becomes the most imperative need in an addict's life. "Drugs are a more powerful reinforcer than anything else, even sex," says Volkow. "That's why people will even steal to get the money they need for drugs. That's one of the unfortunate consequences of a pathology in the brain that makes us lose our judgment, our values."

One of the main challenges going forward, she said, it to figure out how to increase dopamine receptors in those with low receptor levels. It appears that levels are affected by both genetics and experience; for example, animal research indicates that receptors decrease when the subject experiences high levels of stress, and go up when the stress is relieved. Whether that will hold true in humans, and whether some people are more sensitive to this reaction under stress, is as yet unknown.

But Volkow says that may explain why some can drink or use a drug for years and not get addicted, but "then something tragic happens, and they become vulnerable. Some people are born with a great vulnerability; for others, it takes years and years, until their environment and genetics collide in an adverse way," she says.

Volkow hopes that as we learn more about addiction, curing it will become a higher priority. "I've never met anyone who thought they would become addicted," she says. "They always say that this is the last thing they thought would happen to them, because they have such a strong will. But this disease robs you of free will. The challenge is to find a cure."

© 2006