As teenagers, the biggest things many of us had to worry about were deciding which home hair dye colour to buy next and which cryptic song lyric to use as our MSN name.But the world is a different place for teenagers these days and, according to new research, girls in the UK are increasingly unhappy.A report by the Children's Society says 34% of girls aged 10 to 15 are unhappy with their appearance and 14% are unhappy with their lives as a whole, the BBC reported The charity's annual Good Childhood Report for 2016 includes figures for England, Wales and Scotland for 2013-14 and compares how girls' happiness levels have changed since 2009-10.In 2009-10, around 11% of both boys and girls said they were unhappy. However, a sharp gap has opened up between boys and girls, with the proportion of unhappy girls rising to 14% while the figure for boys remained stable.Girls are also increasingly preoccupied by their appearance, the research found. The proportion of girls worried about their looks grew from 30% to 34% in 2013-14. By contrast, the proportion of boys who reported the same feeling remained stable at 20%.The report used data from the Understanding Society Survey , which gathers information from 40,000 UK households. The Children's Society and researchers from the University of York then analysed teenagers' responses."This isn't something which can be explained away by hormones or just the natural course of growing up," Lucy Capron from the Children's Society told the BBC , adding that the findings need to be taken seriously and acted upon.She suggested that social media – and how it is used in relationships – may have contributed to girls' increased unhappiness over time. "Some other research has shown that girls are spending a lot more time on social media - up to three hours a night in some cases - and we need to make sure that's done in a safe way," Capron told the BBC.One 15-year-old girl, who has recently struggled with an eating disorder and depression, said social media, academic stress, peer pressure and body image ideals all contribute to how she feels about herself and her life as a whole."Social media can make me unhappy when something goes wrong because there's really no escape. Even if I turn my phone off the messages will still be there and I can't ignore them," she told Refinery29.However, she added that it sometimes lifts her mood. "I feel very connected to my friends when I'm using it and so I'm much happier with it. There are times when I'd be very, very lonely without it. I wouldn't want to get rid of it because I think it brings me more happiness than sadness."She also said there "definitely is pressure to look a certain way," which comes from her peers as well as the mainstream media and visual social media platforms such as Instagram, in particular."Stress from work causes a lot of unhappiness," she added. Referring to her single-sex school, she said: "I think girls especially put a lot of pressure on themselves to achieve the top grades and get very disappointed if they don't. I know I'm unhappy when I don't, even if the grades I've got are perfectly acceptable and good."The stereotypically "moody teenager" may be a cliché and mostly used lightheartedly, but it's clear we need to make the mental health of teenage girls a top priority.