The American Health Care Act — the Republican plan to repeal and replace Obamacare — is projected to lead to 24 million fewer Americans without coverage by 2026.

But the bill will not just leave Americans with physical ailments in the cold. It makes the future of mental health care uncertain for some of the nation’s poorest — the exact people who are most at risk for mental health issues, according to several large studies.

The proposed GOP health care law creates uncertainties for mental health coverage for those who need it most

Under Obamacare, insurance plans have to cover mental health just as they cover physical ailments. That would continue under AHCA, though insurers may be able to pay less for mental health treatments. (More on that here.)

What’s up in the air under the new law is what happens to people who receive mental health coverage via Medicaid.

Around half of the 20 million people who gained health care coverage under Obamacare did so under Medicaid. President Obama’s Affordable Care Act gave money to states to expand Medicaid benefits for the working poor. (To qualify for Medicaid, a single person has to make less than $15,000 a year.)

Here’s a key difference between Obamacare and the proposed replacement: Whereas under Obamacare the federal government mandated which services Medicaid had to cover, under the new health care law, states would be able to decide.

Come 2020, states will be allowed to drop mental health coverage from their Medicaid benefits.

And there may be a financial incentive to do so. The proposed health care law caps the amount of money it sends to states on a per capita basis. (Currently, the federal government has an open-ended obligation to match state spending on Medicaid.) With fewer federal dollars, states might see cutting mental health programs as an attractive cost-saving measure.

Many states may keep Medicaid coverage for mental health. But they’ll need to grapple with the fact that the nation’s poorest are often the most susceptible to mental health issues like mood disorders.

Around 11 million Americans currently receive mental health and substance abuse treatment under the Medicaid expansion. “Removing [the] requirement would cause the loss of coverage for these life-saving treatments to millions of Americans and challenge the health of our nation,” Antonio Puente, the president of the American Psychological Association, said in a statement advocating against the proposed GOP bill.

The nation’s poor are the most at risk for mood disorders and other mental illnesses

People aren’t poor because they have mental health issues. The correlation goes both ways. Poverty is a source of chronic stress that puts us at greater risk for mental and physical ailments.

In 2011, the journal JAMA Psychiatry published the results of a huge study with more than 30,000 participants in the United States who were tracked for three years on measures of income, mental health disorders, and suicidality.

Those in the low-income category were at greater risk for every mental health ailment measured (except for alcoholism): They were two times more likely to have bipolar disorder, two times more likely to have dysthymia (a lower-intensity but longer-lasting form of depression), and 1.39 times more likely to have PTSD and social phobias. See the complete data table here.

The study also collected some longitudinal evidence that suggest financial strain may cause or aggregate mental health problems. Over the three-year study period, participants who fell from high economic status to low were “at significantly increased risk of incident mood disorders; substance use disorders; and any mood, anxiety, or substance use disorders,” the study found. A reduction in income resulted in a 1.5-time risk increase for any mood disorder.

(Yes, the increases in relative risk are small on the individual level. Increasing your risk of depression times two does not mean you’ll get depressed. Your lifetime risk for a depressive episode is around 6/100. Doubling your risk to 12/100 is concerning but not destiny. But when you’re talking about millions of people, you’re talking about great numbers of additional cases of depression.)

Other studies have come to similar conclusions. One meta-analysis of 50 studies found that people of lower socioeconomic levels were around 1.81 times more likely to be depressed than people of high socioeconomic backgrounds. And they found a typical dose-response pattern to the relationship: The greater the poverty, the greater the risk of depression.

Medicaid coverage helps depressed patients

The nation’s poorest may be the most at risk for mental health issues, but they also have the most to gain from treatment. According to the APA, Medicaid accounts for 29 percent of all the spending on mental health.

Overall, Medicaid is in for big cuts. According to the Congressional Budget Office, the GOP will cut $880 billion in federal funds from the program over the next 10 years. By 2026, the CBO estimates, 14 million fewer people will be covered by the program.

When it comes to mental health, Medicaid has been shown to offer effective treatment, particularly for depression. As Vox’s Julia Belluz has reported, the best data on Medicaid’s benefits — from a statewide randomized trial in Oregon — reported impressive gains in depression risk:

Thirty percent of patients in the control group (who didn’t gain Medicaid access) screened positively for depression two years after the state lottery. Among the people who got Medicaid, that number dropped by a third (or 9 percentage points). And we know depression is one of the leading causes of disability in the country, so that impact is a big deal.

The impact of mental illness can feel more abstract than the impact of diseases such as cancer or diabetes. “Unlike cancer, much of the economic burden of mental illness is not the cost of care, but the loss of income due to unemployment, expenses for social supports, and a range of indirect costs due to a chronic disability that begins early in life,” Thomas Insel, former head of the National Institute of Mental Health, explained in 2011.

Mental illness touches every corner of life, and influences our physical health as well. And it’s not hard to imagine it being taken away from the people who can benefit from it the most.