One in five adults have debt from student loans and 57 percent of those are worried they may not be able to repay the balance, according to a study from the Urban Institute’s Opportunity and Ownership Project.

There is $1 trillion in outstanding student loan balances in the United States, according to the Federal Reserve Bank of New York. In 2010 student loan debt held by 29- to 37-year olds was second only to mortgage debt.

The study, Forever in Your Debt: Who Has Student Loan Debt and Who’s Worried? researched by Caroline Ratcliffe and Signe-Mary McKernan, was funded by Finra Investor Education Foundation and used data from the organization’s 2012 National Financial Capability Study.

The research revealed that 9 percent of people with no more than a high school diploma have student loan debt, possibly from non-degree training or to fund a child’s education. Twenty-five percent of those with some college experience, but no degree, have loans, while 30 percent of college grads and 28 percent of those with advanced degrees are in debt.

According to the study, 16 percent of whites, 19 percent of Asians, 28 percent of Hispanics and 34 percent African Americans have student loan debt.

Debt is somewhat equal among income levels, with 18 percent of households earning $100,000 or more having student loans, and 20 percent of households earning less than $25,000 having loans.

However, 72 percent of those earning less than $25,000 annually are concerned about their ability to repay their student loans, twice the rate (36 percent) for those earning above $100,000.

Repayment concerns are more prevalent among people with dependent children, women, people not employed full time, and those with lower household incomes.