Washington ? Addiction isn’t just about willpower. It’s a chronic brain disease, says a new definition aimed at helping families and their doctors better understand the challenges of treating it.

“Addiction is about a lot more than people behaving badly,” says Dr. Michael M. Miller of the American Society for Addiction Medicine.

That’s true whether it involves drugs and alcohol or gambling and compulsive eating, the doctors group said Monday. And like other chronic conditions such as heart disease or diabetes, treating addiction and preventing relapse is a long-term endeavor, the specialists concluded.

Addiction generally is described by its behavioral symptoms — the highs, the cravings, and the things people will do to achieve one and avoid the other. The new definition doesn’t disagree with the standard guide for diagnosis based on those symptoms.

But two decades of neuroscience have uncovered how addiction hijacks different parts of the brain, to explain what prompts those behaviors and why they can be so hard to overcome. The society’s policy statement, published on its website, isn’t a new direction as much as part of an effort to translate those findings to primary care doctors and the general public.

“The behavioral problem is a result of brain dysfunction,” agrees Dr. Nora Volkow, director of the National Institute on Drug Abuse.

She welcomed the statement as a way to help her own agency’s work to spur more primary care physicians to screen their patients for signs of addiction. NIDA estimates that 23 million Americans need treatment for substance abuse but only about 2 million get that help. Trying to add compassion to the brain findings, NIDA even has made readings from Eugene O’Neill’s “Long Day’s Journey into Night” a part of meetings where primary care doctors learn about addiction.

Then there’s the frustration of relapses, which doctors and families alike need to know are common for a chronic disease, Volkow says.

“You have family members that say, ‘OK, you’ve been to a detox program, how come you’re taking drugs?'” she says. “The pathology in the brain persists for years after you’ve stopped taking the drug.”