About half of all kids and teens bite their nails. Many don’t grow out of it, either. If you’re an adult who bites your nails, you may have done it when you were younger and just never stopped.

It could be your parents’ fault: Scientists aren’t sure if nail biting is genetic, but kids whose parents bite their nails are more likely to bite their nails, too. Studies show this happens even if the parents stop doing it before their child is born.

Sometimes, nail biting can be a sign of emotional or mental stress. It tends to show up in people who are nervous, anxious or feeling down. It’s a way to cope with these feelings.

You may also find yourself doing it when you’re bored, hungry or feeling insecure. Most nail biting is automatic — you do it without thinking.