(CNN) More teenagers are identifying themselves with nontraditional gender labels such as transgender or gender-fluid, according to a new study.

The research, published Monday in the journal Pediatrics , found that almost 3% of Minnesota teens did not identify with traditional gender labels such as "boy" or "girl." That number is higher than researchers expected. A UCLA study from a year ago estimated that 0.7% of teens identified as transgender.

Lead researcher Nic Rider of the University of Minnesota said the main purpose of the new study was to examine health differences between gender-nonconforming teens and teens who are cisgender, a person whose gender identity aligns with the sex assigned to them at birth.

The study found that transgender and gender-nonconforming (TGNC) youth reported "reported significantly poorer health" -- including mental health -- than cisgender teenagers. TGNC teens also were less likely to get preventive health checkups and more likely to visit their school nurse, the study found.

But more surprising may have been the rising percentage of teens who say they don't fit traditional gender norms.

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