By the time girls reach age 17, more than one-third of them have experienced depression, according to a new study in the journal Translational Psychiatry. The data was compiled from 100,000 children who participated in the annual National Survey of Drug Use and Health between 2009 and 2014.

It's different with boys. By age 17, only 13.6% of boys experienced depression. Senior researcher Joshua Breslau told The Washington Post that the large gap between boys and girls is partially attributable to something socially or biologically that girls experience during their teen years. However, he noted that the difference is significant as early as age 12, suggesting that the origin of depression begins at an even younger age.

The conclusion: Researchers determined that children who experienced depression function similarly in school, and also showed a similar likelihood of suicide. There is still more to be done to understand why some develop problems later in life and others come out of depression without intervention, study author Elizabeth Miller told the Post. She says it is essential for people who work with children to be able to identity signs of depression.