Their work is the first to try to gauge the mental toll of child marriage, which has already been tied to several health problems, such as pregnancy complications and an increased risk of sexually transmitted infections.

So far, most research has focused on child marriages in low- and middle-income nations in Africa and Asia, where it is often rampant.

But according to the new report, the U.S. also has its fair share of underage brides.

Based on a government survey from 2001 and 2002, it estimates that as many as nine percent of American women took their vows as kids. About 9.4 million women were married at 16 or younger, and 1.7 million were no older than 15.

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Child Marriage Is 'A Major Psychological Trauma,' New Study Says