Half of 13 to 15-year-olds know a peer who is suffering from harm but keep it a secret, research suggests.
Unwelcome experiences are common among the young
Problems like bullying, bad treatment at home, drug and alcohol abuse and self-inflicted harm were widespread, an NSPCC survey of 1,600 teenagers found.
While many young people knew a friend who was in difficulty, many had not mentioned it to an adult because they did not want to betray a confidence.
The charity is launching a campaign to encourage youngsters to seek advice.
Young teens with friends in trouble
Number of 13 to 15-year-olds who know a friend:
Using alcohol or drugs: 38%
Harming themselves: 32%
Being bullied: 23%
With anorexia/bulimia: 23%
Suffering street violence: 19%
With parents fighting: 15%
Struggling with sexual experiences: 15%
The survey found 13 to 15-year-olds were far more likely to know another teenager being harmed than older teenagers.
Thirteen to 15-year-old were:
- Four times more likely to know a friend being harmed through sexual experiences than 16 to 19-year olds,
- Five times more likely to have a friend who is self-harming
- Twice as likely to know another young person being badly treated at home,
Teenage girls (55%) were almost twice as likely as boys (31%) to know someone who was being harmed.
London teenagers were twice as likely than the national average to know another young person was being harmed (81%).
When a friend was in trouble, teenagers were twice as likely to turn to another friend for advice (42%) than to tell their parents (20%). One in 10 would not tell anyone.
A third of young teenagers said they would keep a friend's harmful experience secret as a sign of loyalty while one in four would be worried because they would not know how to help.
The NSPCC is launching a campaign to encourage every child and young person to speak to someone they trust if they have concerns.
Mary Marsh, NSPCC chief executive, said: "It's worrying to learn that for many vulnerable young teens their serious problems remain a secret among friends.
Older teens with a friend in trouble
Number of 16 to 19-year-olds who know a friend:
Using alcohol or drugs: 23%
Harming themselves: 9%
Being bullied: 15%
With anorexia/bulimia: 12%
Suffering street violence: 5%
With parents fighting: 11%
Struggling with sexual experiences: 6%
"Talking to a friend can be a good first step in dealing with problems. However, this can place a lot of responsibility upon young shoulders and put problems out of the reach of adults who are in a position to help.
"We need to take the secrets out of the playground so young people can get the support and advice they need."
The NSPCC is calling on the government to ensure that every child has access in their school to a professionally-supervised peer support scheme where young people are trained to support others.
The society has peer support projects throughout England, Wales and Northern Ireland.
These provide school children with the opportunity to talk about anything worrying them in an environment where an adult is in a position to help.
Mary Marsh said: "Every child needs to have someone they can turn to - someone who will listen, take them seriously and provide suitable advice and support.
"Peer support really can provide that bridge between listening and getting a young person the help they need."
Dinah Morley, of mental health charity Young Minds, said many young people simply did not know what to do when faced with a friend in need.
She said peer support schemes could be effective, but were unlikely to work unless a school created an atmosphere where pupils felt it was safe to talk about sensitive issues.