The American Medical Association calls it a “chronic brain disease.” The U.S. surgeon general calls it a “neurological disorder.” The American Psychiatric Association says it’s “a complex condition, a brain disease that is manifested by compulsive” behavior.

But despite the medical consensus, much of society continues to treat substance use disorder as a lifestyle choice, a voluntary habit, something anyone should be able to change as easily as they change their clothes.

The state’s Department of Corrections will have to defend that attitude in a federal lawsuit that asks whether this disease can be ignored without violating a prisoner’s rights. A decision against the state in this case could make a big difference by putting the best science in the front line of the battle against the opioid crisis.

Zachary Smith of Caribou is suing the state;, with help from the American Civil Liberties Union of Maine. Smith is in treatment for co-occurring disorders, including anxiety, severe depression and opioid use disorder. He has been treated with the addiction drug buprenorphine for five years and does not use illicit drugs. He is scheduled to report to the Maine Correctional Center in Windham as soon as next month to serve a nine-month sentence for domestic violence assault against his father. He has been informed that while he is incarcerated, the state will not allow him to take the doctor-prescribed medication that he needs to control withdrawal symptoms and compulsive cravings for opioids.

More than five years into the opioid crisis, Smith’s situation should not seem novel. Last year, 418 Mainers died of drug overdose, at a rate of more than one a day, and unknown thousands Mainers regularly risk their lives compulsively using very dangerous drugs like fentanyl.

Like Smith, many, if not most, people with drug use disorders also have other mental illnesses that have led them to self-medicate. Many turn to drugs after failing to come to terms with trauma suffered in childhood. They cannot address these underlying conditions while still actively using, so drug treatment is essential to their mental wellness.

For people with opioid use disorder, medication-assisted treatment is considered the “gold standard.” It’s where a drug like methadone or buprenorphine (known also by the brand name Suboxone) is combined with talk therapy, giving patients control of their compulsive behavior so that they can gain control of their lives.

For some, the medicine provides the short-term transition they need to achieve a sober life. Others require years of medication before they can deal with the underlying illness that led to their addiction. Some people may need maintenance for the rest of their lives, allowing them to hold a job and be part of a family as long as they can keep their symptoms at bay.

But in each case, medication-assisted treatment is preferable to substance abuse. And denying medicine to a person in treatment is the same thing as denying that he or she is suffering from a disease.

The lawsuit correctly asserts that forced abstinence is not an acceptable alternative to treating this condition. For one thing, going through withdrawal is painful. And the experience does not stop the cravings that lead people with this disorder to compulsively use opioids when they can get them, which puts Smith at risk of relapse.

A common time for people to fatally overdose is right after they get out of jail, when their physical tolerance is down but their cravings remain high. That’s why it’s important to continue treatment while they are serving their time.

Prisons and jails can’t ignore other chronic conditions. Diabetics still take insulin. People with high cholesterol get statins. People with high blood pressure can be prescribed medication even though their condition may have been brought on by eating too much; of the wrong kinds of food.

Is substance use disorder a disease, or isn’t it? If it is — and that’s what the doctors say — the state should treat it like one.

There’s no confusion from the medical community on this question. Now it’s up to the courts to deliver a consistent message.