CHICAGO — It has been six decades since doctors concluded that addiction was a disease that could be treated, but today the condition still dwells on the fringes of the medical community. Only 1 cent of every health care dollar in the United States goes toward addiction, and few alcoholics and drug addicts receive treatment. One huge barrier, according to many experts, has been a lack of health insurance.

But that barrier crumbles in less than a year. In a major break with the past, 3 million to 5 million people with drug and alcohol problems — from homeless drug addicts to working moms who drink too much — suddenly will become eligible for insurance coverage under the new health care overhaul.

The number of people seeking treatment could double over current levels, depending on how many states decide to expand their Medicaid programs and how many addicts choose to take advantage of the new opportunity, according to an Associated Press analysis of government data. The analysis compared federal data on the addiction rates in the 50 states, the capacity of treatment programs and the provisions of the new health law.