A case won this week before the Maine Human Rights Commission was the easy part for a Brewer man with a mental disability. The more difficult part lies in U.S. District Court — and beyond — as he seeks to overcome the stigma that surrounds mental illnesses.

William Trask of Brewer suffers from bipolar disorder. Formerly employed by General Signal Corp., he went on long-term disability only to find that, for physical illnesses, he was covered until age 65, but the limit on coverage for mental illnesses was a mere 24 months. He calls the disparity discrimination and, Monday, the Human Rights Commission agreed, 3-2.

It should have. The Maine Human Rights Act is clear on what constitutes discrimination. The commission’s investigator cites state law as follows: “It is unlawful employment discrimination, in violation of this act, … for any employer, … because of … mental disability, … to discharge an employee or discriminate with respect to … compensation, terms, conditions, or priviliges of employment or any other matter directly or indirectly related to employment.”

Mr. Trask has a mental disability; an agent — Liberty Mutual — of his employer tells him that because of his type of disability, he will not receive payments beyond two years, though others with physical disabilities will receive payments far longer. Favoring one category of disability over another causes a real financial harm to Mr. Trask in addition to helping perpetuate the stigma around mental diabilities. Fairly straightforward, despite the dissent of two of the commission members. With the commission’s blessing in the plaintiff’s favor and hope of negotiation between the two parties faint, the case heads for federal court where the debate will revolve around how the Americans with Disabilities Act regards mental illness. The battle there is far from concluded, although Mr. Trask’s case appears strong.

The ADA prohibits discrimination against employees with physical or mental limitations, unless doing so creates an undue hardship. To qualify as a person with a disability under ADA someone must have a physical or mental impairment that substantially limits the person in a major life activity, or have a record of or be regarded as having such an impairment. Liberty Mutual stands accused of discriminating against an entire class of disorders. But in Mr. Trask’s case, bipolar disorder, also known as manic depression, is a lifelong illness characterized by wide mood swings from mania to depression. It is often successfully controlled through therapy and medication such as lithium and tegretol. Some courts have concluded that successful treatment of a mental disorder removes the limitation of a major life activity, and keeps it from qualifying under ADA.

One area that should not cause difficulty is the hardship clause. Although Liberty Mutual’s lawyer argued that equality in coverage would “destabilize” the insurance industry, studies from other cases suggest the cost increase to cover mental impairments to the same level as physical impairments is modest. In a recent case in Virginia, for instance, actuary Arthur W. Anderson, citing a Society of Actuaries pilot study concluded that removing the cap on long-term disability insurance for mental impairment would increase premiums by 8 percent. Eight percent may sound like a significant number until one looks at the total amount of the premium: the increase would come to less than $2 a month for an employee earning $50,000 a year. Even that can be offset, he observed, by changing the ending age of the total coverage from 65 to 62.

For Mr. Trask and others with mental illnesses, the battle over parity of benefits will take years and will be fought over seemingly small details of insurance policies. The result, however, is much larger. Slowly, case upon case, society’s distrustful view of people with mental illnesses will change. Science itself is increasingly demonstrating that what people once thought was all in their heads is chemically based, and can be treated as effectively as a broken leg or a heart condition.

Persuading the public — and insurance companies — to this view is what the battle is all about.