For now, some people who have no health insurance or who buy it on their own may avoid purchasing mental health coverage too, or may avoid seeking treatment for things like addiction or depression. This happens for many of the same reasons that there has historically been less mental health coverage than there has been for other illnesses. The earliest objections among insurance providers and employers had to do with whether mental disorders existed at all, according to Howard Goldman, a professor of psychiatry at the University of Maryland school of medicine. Then there were questions about whether treatment actually worked. Next, concerns arose over cost and how often people would avail themselves of costly mental health treatments.

But a subset of adults who have good insurance coverage still avoid treatment for mental illness to this day, according to Edward A. Kaplan, senior vice president and national practice leader for the Segal Company, a benefits consultant that works with many unions. “Culturally, a lot of people driving trucks don’t believe in it and suffer through,” he said. “And a lot of transport unions don’t trust employers and think they will look at it and use it to retaliate against the workers.”

For many of the people who do have mental health coverage, there is now a bit more of it at a lower cost than there might have been five years ago, even if mental health insurance over all remains much less generous than it was many years ago when employees did not pay as much out of pocket. That’s because a 2008 federal law requires employers with more than 50 employees that do offer mental health coverage to have no more restrictions than there are for physical injuries or surgery, and no higher costs.

This so-called parity bill now applies to a crucial provision of President Obama’s Affordable Care Act. Insurance plans in the exchanges that will offer health coverage to millions of uninsured individuals starting in 2014 must cover many items and services, including mental health disorders and substance abuse.

The combination of parity and expanded care is crucial, according to Anthony Wright, the executive director of Health Access, a consumer advocacy organization in California. After all, parity doesn’t do much good if the mental health coverage need only be equivalent to a meager health insurance plan that covers very little.