The counterintuitive trends clearly have something to do with income barriers. The poor are much more likely to report symptoms of depression the study found, but much less likely to receive care.

It is in this context of dramatic treatment disparities that Clinton is making her case for a major mental health initiative from the federal level. But whether it is realistic, politically or financially, is an entirely different question.

The lengthy policy document that Clinton unveiled this week includes many pledges to improve care for mental illness in schools, prisons and community health centers, but included relatively few details on how the plan would be paid for, particularly by a Congress that is expected to be at least partially controlled by Republicans.

“Ultimately, Congress has the final say,” Ronald Honberg, senior policy adviser with the National Alliance on Mental Illness, told Modern Healthcare. “We can only be optimistic ... that the climate will be conducive to action.”

There is some evidence that Republicans will be less hostile to mental health initiatives than other social programs traditionally pushed by Democrats. For one, some Republicans have framed mental health treatment as an alternative to gun control in the wake of the spike in mass shootings in recent years. Rather than focusing on preventing the mentally ill from buying guns, they have argued, the government should focus on preventing mental illness from the get-go.

Recognizing that presidents rarely accomplish everything they promise to do as candidates, some advocates are appreciative that Clinton is emphasizing the issue of mental health, signaling that at least something significant will be done on the issue.

“There is an emerging bipartisan consensus toward action today,” writes Paul Gionfriddo, president of Mental Health America, in a blog post. “This plan rests solidly within that consensus and adds to it. We applaud Secretary Clinton for offering it, and look forward to the day that mental health is truly seen as an essential part of overall health, and the brain as a most essential part of the body.”

But while Gionfriddo applaudes the plan’s emphasis on early interventions and treatment of all types of mental illness, D.J. Jaffe, executive director of mentalillnesspolicy.org, told USA Today that Clinton’s agenda doesn't do enough to address treatment of those who are suffering from the most severe mental illnesses and require more intense care.

"It is the most seriously ill adults — those with untreated schizophrenia and bipolar disorder — who are most likely to become homeless, psychotic, arrested, incarcerated and suicidal," he said. "Our current system prioritizes the least seriously ill and offloads the others to jails. This plan will continue that practice. "