"Although I expected to find racial and class-based disparities, the magnitude of the discrimination working class therapy seekers faced exceeded my grimmest expectations," says Heather Kugelmass, a doctoral student in sociology at Princeton University and the author of the study.

In fact, the discrimination based on perceived income — or against so-called "working class" people — was far worse than that directed at racial groups. Blacks were generally more ignored by therapists than whites, with middle-class black women and men 30 percent and 60 percent less, respectively, likely to receive a call for an appointment than their white counterparts.

But the largest disparity was around income. Among the findings:

• 92 percent of black and white working class callers did not receive a return call setting up an appointment; 72 percent of white middle-class callers did not receive a call back offering an appointment;

• 83 percent of black middle-class callers did not receive a call back offering an appointment.

More than half of the white middle-class callers did receive a call back, as did 49 percent of the black middle-class callers. The numbers for working class callers were 45 percent and 34 percent, respectively.

Even so, Kugelmass was surprised at the overall low callback rates.

"As consumers, or potential consumers, of mental health care, we'd like to think that everyone deserves a response," she says.

The study, she says, revealed a disturbing bias among therapists that contributes to the lack of access some groups have to mental health services.