There’s something that really bothers Stanford psychiatry professor Keith Humphreys. When he thinks of all the years he spends training the next generation of psychiatrists, the enormous investment in medical school and residency, he wants them to devote that education to taking care of people with serious mental illness.

But many of them instead set up a private practice, where they can charge $400 an hour in cash to help people who Humphreys calls “the worried well” –- people who enjoy the self-exploration of therapy but do not necessarily have a mental health problem.

"A minute I spend training that person is a minute of my life wasted,” Humphreys says. “That very well-trained person should be taking care of very, very troubled people. When they don’t, everyone who needs that care loses out.”

Humphreys says this trend of mental health clinicians shunning the health insurance industry and decamping to the cash market dates back 70 years, to the end of World War II.

In 1946, the majority of veterans cared for by what was then called the Veterans Administration were mental health patients, Humphreys says. But there weren’t enough mental health providers to take care of them. So the VA partnered with several medical schools, including Stanford where Humphreys teaches, to train mental health professionals.

Those schools started turning out hundreds and hundreds of psychologists a year. The expansion dovetailed with soaring American affluence -- and soaring American interest in self-exploration.

Having a psychoanalyst became "a sort of status symbol," Humphreys says.

A lot of psychologists who were trained to work in the public sector saw a better financial opportunity and jumped ship. They hung shingles and started their own private practices where they could charge wealthy people much higher rates.

“When you put in a free market in a society where people were very interested in self-exploration, a lot of them went out and did their own thing,” Humphreys says.

The reason this was possible is because of how the overall U.S. health care system was established, Humphreys says. Most people got their health insurance through work. Employers competed with each other for the best employees by offering better benefits.

So the standards for coverage developed over time in a piecemeal, haphazard way.

As health policy evolved, mental health benefits continuously lagged, Humphreys says. Coverage for mental health treatments or hospitalizations was meager or nonexistent.

“We don’t seem to have this problem with cardiology or oncology,” Humphreys says. “You don’t see people lining up to pay cash for those services because the benefits are so low."

This wouldn’t happen in places that have single-payer health systems, like Canada, Humphreys says, because all the health care payments are controlled by the government. Mental health care was baked into that system earlier on.

As a result, people in Canada with more severe mental illness are more likely to get services, according to a study published in the New England Journal of Medicine.

That’s not the case in the U.S. People with less serious mental health conditions get more services here. Humphreys says it's mainly wealthy people who fall into the worried well category, who are consuming psychotherapy.

“If it’s a market where you pretty much have to pay for yourself, the rich are always going to win,” he says.

The growing workforce of psychiatrists, psychologists, marriage and family therapists, and licensed social workers has responded to that market demand.

And not just because it’s better money. Treating high-functioning professionals in a private office is a lot less stressful than doing rounds on a psychiatric ward of a public hospital.

“It’s understandable why someone would say this is really demanding,” Humphreys says. “For my own well-being or professional satisfaction, I’m going to stop doing this and move into doing outpatient psychotherapy with executives from Google who have angst. My salary goes up dramatically and my work is much, much easier.”

Especially in affluent places like the Bay Area, this creates a divide, a culture of mental health haves and have-nots. Mental health clinicians don’t need to participate in the health care system or take insurance to keep their schedules full -- making it harder and harder for people of lower income to find a therapist.

“That’s why you can have a lot of mental health professionals in an area, but still have a shortage of care for people in need,” Humphreys adds. “The person who’s hurt is the person who’s suicidal, maybe they’re horribly addicted to OxyContin or their child is showing signs of bipolar disorder, and they can’t find somebody to take their insurance. It’s unjust.”

Mental health advocates have worked to shift this balance, passing the Mental Health Parity and Addiction Equity Act of 2008 and the Affordable Care Act in 2010. Together, those laws require health plans to offer mental health coverage on par with other medical coverage.

But so far, it hasn’t put a dent in the cash market for mental health. Humphreys says given the nature of mental health care and the American obsession with self-improvement, the cash market will be here to stay.

“Accessing mental health care is often pleasurable and enjoyable, and accessing a lot of other health care isn’t,” Humphreys says. “I mean, who goes to the dentist for fun?”