As a polarizing year nears its end, Americans can be grateful that political progress, though under-discussed, is being made on three important issues. First, Congress and 43 state legislatures have passed legislation to address our nation’s opioid and addiction crisis. Second, Congress may take up bipartisan reforms ­—which, at the state level, have reduced incarceration rates and violent crime simultaneously. Third, as the debt-ceiling debate resurfaces, both parties are once again discussing the need for fiscal discipline.

These steps place federal and state officials on a path to prove that they can govern responsibly in advance of the 2020 campaign cycle. The United States is facing three intertwined, expensive, and emotionally exhausting national crises: substance abuse, mental illness and mass incarceration. We can curtail all of them if we begin to fulfill an obligation that the Constitution, compassion and common sense require. Specifically, by providing people in jails and prisons with the health care they’re legally entitled to, we can save lives, reduce repeat offenses and decrease costs.

Each year, more than 72,000 Americans die of overdoses, and more than 45,000 die of suicide. Nearly 2.2 million individuals are incarcerated in federal and state prisons and in local jails. The human toll of the substance abuse, mental health and incarceration crises is compounded by their economic effect. The combined annual societal costs of overdose, suicidal behaviors and incarceration are in the range of $1.6 trillion. That is 8.2 percent of the $19.4 trillion U.S. GDP.

More than two-thirds of city and county jail inmates have an alcohol or drug problem, and even more — three-quarters — have a mental-health disorder. These individuals have a constitutional right to treatment while incarcerated. In 1976, the Supreme Court, in Estelle v. Gamble, established that deliberate indifference to the serious medical needs of incarcerated individuals constitutes cruel and unusual punishment and violates the Eighth Amendment to the Constitution.

Nevertheless, the norm nationwide is not to provide individuals who have substance-use problems and mental-health disorders adequate treatment while they’re incarcerated. Inmates with opioid-use disorder are typically detoxed without medication, and those with mental-health disorders like schizophrenia are often put into solitary confinement, where their conditions can worsen rapidly. In the civilian world, by contrast, the medical standard of care for opioid-use disorder and schizophrenia is typically a combination of medication and counseling tailored to meet the patient’s unique needs.

Incarceration can be said to serve two purposes: retribution and rehabilitation. Denying adequate health care to incarcerated individuals with substance-use and mental-health disorders fails at both objectives. It exceeds the bounds of acceptable punishment by denying relief of dreadful symptoms. It also leaves individuals worse off, and means they will re-enter their communities at greater risk of overdosing or with even more severe mental illness.

Budgets, not cruelty, are the primary justification for the failure to provide adequate substance abuse and mental-health treatment in jails and prisons. Private health insurance is typically cut off when a person is detained. Under federal law, Medicaid and Medicare coverage are also discontinued. Correctional institutions have their own health care budgets, and treating complex brain disorders can overwhelm their finances unless the facilities find corresponding cost savings, which isn’t an easy task.

Experience proves that providing modern-day treatment to individuals with substance-use and mental-health disorders decreases repeat crime and incarceration and their related costs.

Rhode Island — which had the nation’s seventh highest opioid overdose death rate — began in 2016 following current standards for treating people with opioid-use disorder both during and following their time in jail. The Rhode Island program includes medication, therapy and assistance in finding jobs and housing. The results of this program have been remarkable. The state has seen a 61 percent decrease in drug overdoses among recently incarcerated individuals.

Similarly, a 2015 study published in the Journal of Clinical Psychiatry found that using injectable medication to treat people with schizophrenia who had been previously incarcerated helped keep them out of jails, prisons and hospitals for a median of 416 days. The medication costs $83 per day; using it is estimated to save the prison systems $99 per day, a $16 daily savings.

These studies illustrate what most Americans know by common sense: When humans lead healthy, secure and productive lives, crime goes down, and so do taxpayer costs.

We already have the models to address the intertwined crises of substance abuse, mental illness and mass incarceration. With big-picture budgeting and bipartisan action, we can address these issues in a way that also supports yet another neglected population: the 72 percent of Americans calling for fiscal responsibility.