The UK has a nation of "deeply unhappy" youngsters, a children's charity has warned, as it suggested many young people are dealing with fears and worries that did not exist 30 years ago.
ChildLine, which is marking its 30th anniversary, suggested that modern-day pressures such as cyber-bullying and social media are affecting children's confidence and self-esteem.
In 1986, when the 24-hour helpline began, children's top concerns were sexual abuse, family problems, physical abuse and pregnancy, according to ChildLine's figures.
Last year, the main issues raised were family relationships, low self-esteem and unhappiness - which was not recorded at all 30 years ago, bullying, including cyber-bullying and self harm, which also did not feature in 1986.
Overall, 35,244 of the counselling sessions held by the NSPCC-run service in 2014/15 were related to low self-esteem and unhappiness - up 9% on the year before, according to new figures published by the organisation.
There has also been a leap in the overall number of sessions the helpline runs each year, going from 23,530 in 1986/87 to 286,812 in 2014/15.
NSPCC chief executive Peter Wanless said: 'It is clear from the hundreds of thousands of calls ChildLine receives that we have a nation of deeply unhappy children.The pressure to keep up with friends and have the perfect life online is adding to the sadness that many young people feel on a daily basis.
"The worries that young people face and the way they talk to us have dramatically changed since ChildLine was launched, and we will change to make sure that no matter what, young people will have a place to turn to whenever they need it. Times may change but one thing stays the same - our vital helpline is often the only place that many young people feel they can turn to."
One 13-year-old girl told a counsellor: "I hate myself. When I look at other girls online posting photos of themselves it makes me feel really worthless and ugly. I'm struggling to cope with these feelings and stay in my bedroom most of the time."
A 12-year-old girl said: "I feel like crying all the time. I'm constantly worried about what other people are thinking of me and it's really getting me down. I use social media sometimes but that just makes me more depressed as I hardly have any friends online and no one likes my posts/photos."
The NSPCC said that the way that children contact ChildLine has also shifted. While 30 years ago, youngsters got in touch by using public telephone boxes, home landlines or writing letters, now they are more likely to opt for an online chat or send an email.
Less than one in three of ChildLine's counselling sessions were via the telephone last year, the charity said, while 71% involved email or online chat.
Dame Esther Rantzen, founder of ChildLine, said: "It is thanks to the skill and commitment of generations of ChildLine staff and volunteers over the last 30 years that we have been able to help more than 4 million children. But it is a national tragedy that British children are so unhappy.
"I remember in 1986 how shocked we were to discover that so many children were suffering terrible abuse in their own homes. But today I am shocked by the acute unhappiness and loneliness that afflicts so many young people which means that, for many, the only place they can find comfort and protection is from our helpline."