A third of teens and young adults have self-harmed at some point in their lives, a new poll suggests.
A survey of 1,000 16 to 25-year-olds from across the UK found that 36% had self-harmed.
The poll, released by Self-Harm UK, The Mix and YoungMinds, also found that only 46% would be confident knowing what action to take if a friend did open up to them about their self-harm.
The charities have released tips on how people can help someone who tells them they are self-harming.
These include offering to listen, helping them find support, being there for them in the long-term.
Youngsters should "not panic" if they are unsure how to react and "often simply being there is enough", the charities said.
Chris Martin, chief executive of The Mix, said: "It is shocking that self-harm remains so prevalent among young people as they struggle to manage their emotional wellbeing.
"What is clear from this survey is that peer support can potentially play a huge role in helping young people to recover.
"We need to do more to ensure that all young people know where they, or their friends, can turn when they self-harm and how peer groups can play their part in supporting those who are affected."
Sarah Brennan, chief executive of YoungMinds, added: "While this poll does not explain in what ways young people harmed themselves or whether they did it once or regularly, it is clear that this is a huge problem in our society that needs to be addressed.
"We know from calls to our Parents Helpline how overwhelming it can be if you find out that a child or young person is self-harming.
"But by offering the right support, friends and family can make a huge difference."
:: For more information visit www.selfharm.co.uk, www.themix.org.uk or www.youngminds.org.uk.