A bill that would require health insurance companies to cover mental illness and substance abuse treatment at the same level as other ailments stands its best chance ever of becoming law.

Measures seeking mental-health parity have been introduced at the state Legislature for almost two decades. Rarely have the bills made it out of committee, beaten back by opposition from small businesses and the insurance industry.

But key lawmakers breathed new life into the issue late last week, reintroducing the measure in the Senate Health Committee, which passed it 5-1.

House Bill 2209 wouldn’t force health plans to offer mental health coverage, but insurers that do would be forbidden from charging higher co-payments and deductibles or putting stricter limits on hospital stays and other behavioral-health treatment.

Arizona is one of nine states without mental health parity.

“I believe that this is the year that Arizona finally stops discriminating against the brain,” said Rep. Ed Ablesar, D-Tempe, the bill’s sponsor.

Ablesar, a school counselor, said the current system enables adults and children to get plenty of drugs under their private insurance plans — generally prescribed by family physicians and pediatricians — but limits the amount of talk therapy they can receive.

The combination of medication and therapy is considered the most effective treatment for depression and other mental illnesses, particularly in children and those also struggling with substance abuse.

But the larger issue underlying the parity debates in Congress and in statehouses across the country centers on the notion that treatment for the brain is somehow different than the rest of the body.

Now research shows that integrating physical and behavioral health care makes sense both medically and financially, resulting in better outcomes and lower health care costs.

Parity opponents, including the National Federation of Independent Business and private health insurance companies, argue that broadening mental health and drug and alcohol abuse coverage would drive up insurance premiums as people flock to treatment.

Small businesses that now provide some mental health benefits to their employees might not be able to afford to offer a beefed-up plan, said Michelle Bolton, state director of the federation.

“Wouldn’t you rather have some mental health coverage than nothing at all?” Bolton said. “They can’t offer something that’s pared back.”

Bolton said Arizona small businesses already find it increasingly difficult to afford health insurance for their workers and fear additional requirements will put it out of reach.

The bill wouldn’t allow unlimited visits or treatment that isn’t deemed “medically necessary,” said Sherri Walton of the Mental Health America’s Arizona chapter.

Just as the level and duration of treatment for high blood pressure or heart disease varies with each patient, so too does treatment for depression or schizophrenia.

Opponents also argue that people who abuse drugs and alcohol should pay for those choices and not pass those costs on to all policyholders.

Supporters of HB2209 testified last week that nearly two-thirds of those addicted to drugs or alcohol are found to have an underlying mental illness.

“They self-medicate,” Walton said. “You can’t treat one without the other because they won’t get well.”

Both sides cite studies to support claims that parity will affect insurance premiums.

A widely publicized 2006 study of the parity plan offered to members of Congress and federal employees found that it didn’t drive up costs as insurers had predicted.

Bolton pointed to other studies that showed premium increases of up to 5 percent with mental health parity. But she also said research on the federal program and those of other states have no merit here.

She wants Walton and parity supporters to produce an actuarial analysis of the bill’s potential impact, as proponents of an autism bill did earlier this session.

That bill, signed into law by Gov. Janet Napolitano last month, requires insurers to provide coverage for autism treatment, but exempts businesses with fewer than 50 employees. Walton said a similar exemption could be added to the mental health parity bill.

Although most Arizona members of the National Federation of Independent Business have fewer than 20 employees and could qualify for the exemption, Bolton said they’ve also been clear that they oppose insurance mandates.

“I’m tired of being told that we are anti-mental health. That’s not the issue. The issue we are against is mandates,” she said.

“We are in a crisis right now,” Bolton said. “My members are the angriest I’ve ever seen them with regards to health insurance.”

The autism bill may have paved the way for mental health parity.

Ablesar said he was initially concerned about singling out a behavioral health condition for coverage, but believes that the autism debate — and testimony from parents and children — opened lawmakers’ minds.

“It helped promote a more empathetic concept of mental illness,” he said.

Beyond that, Ablesar said, both bills will wind up saving taxpayer money as more families will get better access through private insurance and not rely on state programs for treatment.

“The people who objected to it because of financial considerations will see that this actually takes it in the other direction and will save tremendous amounts of money,” he said.

“We don’t have a system in place to truly confront and fight depression. With this bill, we will have it.”

The bill now goes to the full Senate, where it faces its toughest test. If it clears that body, supporters believe they have the votes in the House and the support of the governor.