The number of children and young people self-harming has risen dramatically in the past 10 years, new NHS figures obtained by the Guardian show.

The sharp upward trend in under-18s being admitted to hospital after poisoning, cutting or hanging themselves is more pronounced among girls, though there have been major rises among boys too.

Experts say the rise is shocking confirmation that more young people are experiencing serious psychological distress because they are under unprecedented social pressures.

The number of girls under 18 who have needed hospital treatment after poisoning themselves has gone up from 9,741 in 2005-06 to 13,853 – a rise of 42% – figures collated by NHS Digital show. The numbers of boys ingesting a poisonous substance have stayed almost unchanged; 2,234 did so in 2005-06 and 2,246 did so in 2014-15.

However, the number of girls treated as inpatients after cutting themselves has almost quadrupled over the same period, from 600 to 2,311 – a 285% rise. The number whom A&E teams have treated after hanging themselves has also risen during that decade, from 29 to 125.

While far fewer boys end up in hospital after cutting themselves, the numbers went up from 160 in 2005-06 to 457 in 2014-15 – a rise of 186%. Similarly, the numbers of boys who hanged themselves also doubled from 47 to 95 over the same period, the figures show.

“This is a depressing confirmation of the clinical experience of child and adolescent psychiatrists’ experience on the ground,” said Dr Peter Hindley, chair of the Faculty of Child and Adolescent Psychiatry at the Royal College of Psychiatrists.

“It is also shocking because it appears to confirm our clinical experience that levels of distress are rising, though not all young people who self-harm have mental health problems, and [that] mental health disorders are rising, for both girls and boys,” he said.

Experts said the rises were likely to be due to a variety of factors, including pressure to succeed at school, the damaging effects of social media, family breakup, growing inequality in recent years, children’s body-image fears, a history of abuse, including sexual abuse, and increasing sexualisation.

The NHS’s most senior doctor responsible for young people’s health said the distressing figures underlined that greater improvements were needed to boost support for troubled children.

“It’s clearly distressing that more young people are causing harm to themselves and we know that the problems facing children are growing,” said Dr Jackie Cornish, NHS England’s national clinical director for children, young people and transition to adulthood.

“In common with most experts, we believe this is due to increasing stress and social pressure on young people, including to succeed at school, and emerging problems with body image leading to eating disorders and self-harm.”

She added: “We recognise that vital care for children and young people’s mental health is an area where more work needs to be done.”

Jeremy Hunt, the health secretary, severely criticised NHS care of troubled young people last week. Child and adolescent mental health services (CAMHS) were the “biggest single area of weakness in NHS provision” and beset by “big problems”, including failure to intervene early enough when problems such as eating disorders emerged, which meant that “too many tragedies” were occurring, he said.

Hindley added: “The rise is likely to be as a result of many factors but the most important ones are likely to be: growing inequality in the age of austerity, the negative impact of the digital age, increasing sexualisation – this is particularly important for girls – and the impact of abuse and sexual exploitation, and increased pressure to succeed.”

Sarah Brennan, the chief executive of Young Minds, said that troubled young people were harming themselves partly because help for them is so inadequate that some do not receive specialist support once it is obvious they have psychological problems. “It’s extremely worrying that the number of young people needing hospital treatment for self-harm has risen so sharply. There needs to be far more investment in early intervention, so that problems are dealt with when they first emerge.”

Budget-driven local council cuts to social workers, educational psychologists, parenting classes and mental health services in schools had reduced care and support for under-18s in distress, she said. CAMHS teams were responding to rising demand by rationing care.

“The pressure on CAMHS has forced services to raise the bar for access to treatment. Consequently, about a quarter of young people are being turned away, and this will include many who self-harm. At the moment too many vulnerable children end up going to A&E because no other help is available,” Brennan added.

Young Minds is concerned that children who self-harm and then turn to the internet for help could come across unhelpful information about, and even encouragement to continue, their behaviour. Young people who self-harm are most likely to go online for information and few seek their parents’ support, according to a survey it conducted in March with Childline, Self-Harm UK and The Mix. While 76% of youngsters said they would search the web, just 16% would look to their mother or father, while 61% would ask a friend, and 27% cited a GP and 17% a teacher.

The government has promised to put an extra £1.4bn into care of troubled children during this parliament to ensure that at least 70,000 more under-18s get high-quality care. However, NHS England chief executive, Simon Stevens, has admitted that even if that target is met, it will still only increase the proportion of young people being helped from a quarter to a third.

Hunt last week pledged to make children’s mental health a top priority. Cornish added that NHS England has created 56 extra beds in specialist inpatient units for children and young people in the last two years and is putting £30m into improving services for those suffering from an eating disorder such as anorexia nervosa. Earlier this month, it allocated £25m to help cut young people’s waiting time for treatment and reduce the backlogs of those awaiting urgent care.

NHS England collated the figures it shared with the Guardian from those covering self-harm and self-poisoning from its Hospital Episodes Statistics datasets from the past decade.

• In the UK, the Samaritans can be contacted on 116 123. In the US, the National Suicide Prevention Hotline is 1-800-273-8255. In Australia, the crisis support service Lifeline is on 13 11 14.

• This article was amended on 31 October 2016 to correct two percentage figures.