Student use of credit cards is now significant not just for living expenses, but for academic expenses, according to a new study.

A nationwide survey by Smith College researchers found that 23 percent of students are using credit cards to pay for tuition and fees and 52 percent are using them for textbooks and school supplies. Because most students use credit cards as a means of debt, that means that many are paying interest rates that far exceed those of student loans.

More students in the survey had credit card debt than had student loans -- 65 percent compared to 48 percent. And 65 percent of the students with credit cards had two or more cards.

"Students are not just paying for late-night pizza with their credit cards, they are paying for college," said Mahnaz Mahdavi, a professor of economics at Smith and the lead author of the study. "That can be an expensive way to get an education."

Other data from the survey -- which was of 700 students, undergraduate, graduate and professional:

• Students owed an average $2,400 on their credit cards.
• Half of the students reported charging their cards to the limit some or most of the time.
• Twenty-three percent of students who paid tuition by credit card had debt greater than $5,000, compared to 11 percent of those who did not.
• In addition to tuition, textbooks and school supplies, students used their credit cards to pay for the following: personal items (58 percent), dining out (50 percent), entertainment (48 percent),  groceries (47 percent) and travel (33 percent).

One problem the Smith researchers found was that 72 percent of those who responded were women, so the results may be skewed toward female students. (While the study was focused on all college students, the Smith center that sponsored it is called Women & Financial Independence and that name may have discouraged men from answering.)

In comparing the women and men in the survey, the Smith researchers found that women were more likely than men to have credit card debt over $5,000, pay late, and not pay their balances in full.