There are “concerning signals” about the effect of the pandemic on children and young people, researchers have said.

In an editorial published in The BMJ, experts said the mental health of the children of Britain was “deteriorating before the pandemic”.

Known triggers for self-harm and poor mental health are aggravated by pandemic restrictions, they said.

Researchers from the universities of Cambridge, Bristol and Swansea said that between 2004 and 2007 anxiety, depression and self harm increased, particularly among teenage girls.

They said research suggests that probable mental health conditions among children and young people rose from 11% in 2017 to 16% in July 2020.

A separate survey found parents reported deteriorating mental health and increased behavioural problems among children aged four to 11 between March and May last year.

“Studies carried out during the pandemic suggest that although some families are coping well, others are facing financial adversity, struggling to home school and risk experiencing vicious cycles of increasing distress,” they wrote.

They cautioned that both studies linked levels of deprivation with mental health, adding “a stark warning given that economic recession is expected to increase the numbers of families under financial strain”.

They added there is a “possible unmet need” for patients for self harm, adding: “Known triggers for self-harm and poor mental health are aggravated by pandemic restrictions, including separation from friends, arguments with parents, unresolvable arguments on social media, strained finances, academic stress and feelings of isolation.

“School closures are particularly difficult for families facing other adversities.”

Meanwhile, urgent referrals for eating disorders have doubled in 2020 in England.

On suicide, they wrote: “Early data from England’s national child mortality database for March 23 to May 17 2020 raised concerns about suicides among young people aged under 18 years during the first lockdown, although numbers were too small (25 deaths) to be definitive.”

They concluded: “The evolving consequences of the pandemic are set against long-standing concerns about deteriorating mental health among children and young people, and the inadequacy of service provision.

“Although children are at lowest risk of death from Covid-19, concerning signals remain about the pandemic’s effects on their mental health, which are unevenly experienced across different age groups and socioeconomic circumstances.”

In a linked opinion piece, Louis Appleby, who researches suicide and self-harm at the University of Manchester, said the pandemic has had “little effect” on suicide rates.

Drawing on a new monitoring tool set up to assess suicide numbers, he said: “We now have ‘real time surveillance’, recording deaths by suicide as they happen, providing figures for a population of around nine million, one sixth of the country.

“Here, too, we have found no increase in the months post-lockdown.

“The same appears to be true of self-harm.”

Looking forward as restrictions are lifted, he cautioned “recovery can be a dangerous time”, adding: “We need to ensure support for anyone lonely or mentally ill, in turmoil or financial hardship.”

Professor Prathiba Chitsabesan, NHS England’s associate national clinical director for children and young people’s mental health, said: “The NHS has stepped up its support for children throughout the pandemic including introducing 24/7 crisis support lines, face to face, telephone and digital appointments, and I would encourage anyone worried about themselves or a young person to talk to their GP, health worker or a teacher at school, and if you are facing a mental health crisis please call your local 24/7 NHS all-age mental health helpline.”