The number of children admitted to acute hospital wards in England due to serious concerns over their mental health has increased by 65% in a decade, with a particularly alarming surge in girls who have self-harmed, research reveals.

Doctors are treating almost 40,000 children with acute mental ill health in general wards every year, up from about 24,000 10 years ago. The increase is six times higher than the rise in admissions of children for all conditions (10.1%) over the same period.

The Guardian previously revealed how soaring numbers of children were seeking help for mental health conditions, including some who need emergency treatment because they had to wait too long for regular NHS care. The Covid-19 pandemic, social inequality, austerity and internet-related harm are among a range of factors fuelling the crisis.

A new study published in The Lancet Child & Adolescent Health journal sheds light for the first time on how rising numbers are being admitted to acute hospital wards because of clinical concerns over the state of their mental health.

General acute medical wards are specialised hospital wards designed to provide rapid assessment, treatment and care for patients. The units serve as a bridge between emergency departments, GPs, and other wards and are separate from specialised mental health wards such as eating disorder units.

The study’s senior author, Dr Lee Hudson of UCL, said: “Over the past decade, we’ve observed a significant rise in mental health admissions among children and young people to acute medical wards.

“Although there has been attention paid to increased referrals to community mental health services and inpatient mental health settings, admissions to general acute medical settings feels like a piece of the jigsaw missing in the story.”

Acute wards are increasingly playing an especially vital role in caring for children with coexisting physical and mental health problems, such as starvation from an eating disorder, Hudson said.

“However, the increased intensity we describe is presenting real challenges for acute wards, both for patients and their families and the staff supporting them. They may not be set up with an appropriate ward environment for this care, and sometimes staff working there need more training and support with relevant skills.”

Hudson and his colleagues found mental health admissions of five- to 18-year-olds to acute wards increased 65% from 24,198 in 2012/13 to 39,925 in 2021/22. More than half (53.4%) were due to self-harm, according to the analysis.

By comparison, there was a 10.1% rise in all-cause admissions over the same period, from 311,067 to 342,511.

Dr Karen Street of the Royal College of Paediatrics and Child Health said the 65% rise provided further evidence of the “alarming deterioration” in the mental health of children and young people.

The rise in mental health admissions was particularly steep in girls aged 11 to 15, with the study also highlighting “steep relative increases” among children aged five to 10 and “striking rates of self-harm in females”.

There was also a hike in annual admissions for eating disorders, which grew from 478 to 2,938.

Of the 239,541 children and young people admitted for mental health concerns between 2012/13 and 2021/22, 13.4% were admitted again within six months.

Hudson and his colleagues are trying to figure out why more and more children are being admitted to acute medical wards for mental health reasons, he said.

“But it’s likely the bigger background prevalence of mental health problems, and possibly increased severity of individual cases, leading to increased presentations to hospitals that require an emergency admission to a general ward because it is not safe for the patient to go home.”

The analysis showed the increases were not solely due to the pandemic, as there had been year-on-year increases in the number of admissions since 2012, Hudson said.

“This is an issue that appears to now be core business for acute wards, and isn’t going to go away, so a focus on improving care is essential.”

England’s mental health director, Claire Murdoch, said the NHS had responded to record numbers seeking help by rolling out hundreds of mental health teams in schools and offering 24/7 crisis support via 111, but sometimes an admission to hospital was in their best interest so they could get “intense specialist support” and cut the risk of harm.