Girls are twice as likely to suffer teenage angst than boys of the same age, according to research by a think tank.
Demos said analysis of Government statistics suggested as many as 900,000 were "unhappy and depressed" and that young females' moods had darkened sharply in recent years.
Almost a third (30%) described their mindset as being that way rather or much more than usual - twice the rate among young men.
The same differences were found when asked about feeling "worthless" (16% to 7%) and about losing confidence (23% to 12%).
A separate poll by the thinktank - commissioned for a report on the issue being published on Friday - showed a significant decline since 2009.
In that time, the number of teenage girls saying they felt "very happy" slumped from 34% to 17% while the proportion "not very happy" rose from 9% to 16%.
A fifth of those from poorer backgrounds said they were not very happy "most of the time", up from 12% last year.
Julia Margo, Demos Deputy Director, said: "Growing up has always been tough but our research shows that this generation of teenagers has more reason to wallow and fret than previous generations. It is definitely tough to grow up in Britain as a girl and it harder having to do it now than it has been in recent years."
YouGov surveyed a representative sample of 505 women aged 16-19 across the UK between 8-15 March 8-15.
The other findings were drawn from Wave 2 of the Longitudinal Survey of Young People in England and the GirlGuides UK/Childwise 'Girls Attitude Survey' from 2009 and 2010.