Credit cards, student loans, mortgages, car payments—today’s millennials have more debt than ever, and studies show that there can be a long-term health effect on the stress this causes.

Two-thirds of millennials aged 23 to 35 have at least one source of long-term debt, while one-third have more than one source. Average student loan debt in the United States amounts to $40,000, while 37 percent of Americans younger than 40 have accrued student loan debt. Student loan debt in the United States is higher than any other kind of non-mortgage debt in the United States, and according to a recent report from the Consumer Financial Protection Bureau, student loan debt now totals more than $1.2 trillion. More than 40 million Americans, more than Canada’s entire population, have student loan debt.

And, debt alone isn’t the only cause for stress. Misinformation is a contributing factor. Sixty-seven percent of millennials reported they did not receive adequate information about loans before taking them, while 47 percent of private loan borrowers could have borrowed in less risky, more affordable ways. An astounding two in five student loan borrowers are delinquent in the first five years of entering repayment, and 54 percent of millennials over the age of 30 are worried about repaying their student loans, leading to long-term effects between debt and mental health.

New research, led by the University of Southampton, has shown that people in debt are three times more likely to have a mental health problem than those not in debt.

Thomas Richardson, M.D., a clinical psychologist at the university, said in a statement: “This research shows a strong relationship between debt and mental health; however it is hard to say which causes which at this stage. It might be that debt leads to worse mental health due to the stress it causes. It may also be that those with mental health problems are more prone to debt because of other factors, such as erratic employment. Equally it might be that the relationship works both ways.”

Richardson said that a mental condition such as depression could both spur debt and also make debt worse. “People who are depressed may struggle to cope financially and get into debt, which then sends them deeper into depression.”

The review of 65 studies, published in the journal Clinical Psychology Review, showed that the likelihood of having a mental health problem is three times higher among people who also have debt, compared with people without debt. Researchers found that fewer than nine percent of people without mental health problems were in debt. Meanwhile, more than 25 percent of people with a mental health problem were in debt.

People who struggle to pay off debts are twice as likely to experience depression and anxiety, and 29 percent of people with high debt stress report severe anxiety. People with high debt are three times more likely to suffer from mental illness. Stress-related illnesses include ulcers, digestive tract problems, migraines and even heart attacks.