(CNN) There has been a significant climb in the prevalence of major depression among adolescents and young adults in recent years -- and the troubling trend may be strongest in teenage girls, according to a new study.

However, the number of adolescents receiving treatment does not appear to follow that same trend, suggests the study, published in the journal Pediatrics on Monday.

"Although a recent federal task force recommended screening for depression in young people 12 to 18 years of age, screening is far from universal," said Dr. Mark Olfson, a professor of psychiatry at Columbia University Medical Center and a co-author of the study. "The new study highlights that most adolescents with depression do not receive treatment for their symptoms and underscores the need for increased attention to this condition."

The national Preventive Services Task Force recommended in February that all primary care doctors, including pediatricians and family physicians, should routinely screen adolescents for depression.

The new study included data on major depressive episodes and depression treatment, from 2005 to 2014, among 172,495 adolescents and 178,755 young adults across the United States.

The adolescents were 12 to 17 years old and the young adults were 18 to 25 years old when the data were collected. The data came from the National Surveys on Drug Use and Health

After analyzing the data, researchers discovered that the prevalence of major depressive episodes over a 12-month period increased among girls from about 13% in 2005 to about 17% in 2014. The increase was much lower among boys, rising from about 4% in 2005 to about 6% in 2014.

Depression on the rise; teen girls most at risk

Why is depression increasing faster among adolescent girls than boys? More research is needed to find a definitive answer, Olfson said.

"While it is not possible to determine the reasons for this difference, cyberbullying may play a role. Negative texting experiences appear to be more common in girls than boys and have been linked to depressed mood," he said.

Bullying was called "a major public health problem" in a report released in May by the National Academies of Sciences, Engineering, and Medicine

Additionally, adolescent girls may face more interpersonal stress -- such as the stress of fighting with a family member or friend -- than boys, putting them at a greater risk of depression, according to separate research published in the journal Clinical Psychological Science in 2014.

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The research involved 382 adolescents who were asked to complete assessments about their thoughts, stressful life events and depressive symptoms. The adolescents completed an initial assessment and then three follow-up assessments, all of which were spaced about seven months apart.

"This is the first study to demonstrate the sequential pathway through which greater exposure to stress and prospective levels of rumination explain the sex difference in depressive symptoms in adolescence," the researchers wrote in Clinical Psychological Science.

'More clearly needs to be done'

Now, according to the new study in Pediatrics, the prevalence of major depressive episodes overall jumped from about 9% in 2005 to about 11% in 2014 in all adolescents and from about 9% to about 10% in young adults.

"Despite the increase in depression among adolescents, the proportion who received treatment remained little changed. This means that there are a larger number of depressed adolescents who are not receiving treatment. More clearly needs to be done to improve access to depression care for young people in the United States," Olfson said.

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An editorial commentary, which accompanied the study in the journal, urged a prioritization of youth depression in the United States.

"The causes behind a rise in adolescent depression should be investigated scientifically," wrote the co-authors of the editorial, Dr. Anne Glowinski, a professor of child psychiatry at Washington University in St. Louis, and Giuseppe D'Amelio, a medical student at the university.

"The other problem, that of ever-increasing untreated youth depression, concerns all of us at a time when suicide is now the second leading cause of death for adolescents aged 15 to 19 years," the editorial said. "Depression is a sizable and growing deadly threat to our US adolescent population."