“Talking therapies” services run by the NHS will be overwhelmed in the autumn when almost 500,000 people who did not get treated during the lockdown finally seek help, according to a major therapy provider. The warning comes as teachers predict a wellbeing crisis among children when schools return full-time in September.

Analysis by Ieso Digital Health claims there will be “an explosion” this autumn in the number of people being referred by their GP for treatment for anxiety, depression and obsessive compulsive disorder. The sharp rise in people suffering psychological conditions during the pandemic will leave England’s 54 specialist NHS mental health trusts struggling to cope.

The NHS has treated far fewer patients than usual since March under its Improving Access to Psychological Therapies (IAPT) programme, which usually gives people face to face counselling. Before Covid-19 struck about 150,000 people a month were referred to IAPT services in England, either by their GP or by seeking help directly themselves.

When lockdown began many NHS services were suspended and many people either became afraid to access care as normal or stayed away in order not to bother the NHS. Research by Ieso shows that in April – the first full month of lockdown – fewer than 60,000 referrals were made. It estimated that by the end of September just over 470,000 fewer people than would have been expected will have been referred since the start of lockdown. If all are referred for care in October, when IAPT services reopen, then that would leave services facing over four times the usual number of referrals.

“One reason referrals to IAPT dropped during the pandemic is that people who were at home because of the lockdown were really worried about having a phone or video consultation rather than a face to face appointment,” said Sarah Bateup, Ieso’s chief clinical officer, who is also an experienced cognitive behavioural therapist.

“Other people didn’t seek a referral because they didn’t want to go to their GP, or decided not to make a fuss because the NHS was so busy. Others were more worried about Covid and keeping their family safe than they were about seeking treatment for anxiety, depression or OCD.”

Ross O’Brien, the digital innovation director at Central and North West London NHS Foundation Trust, one of the country’s biggest mental health trusts, said: “There is the real risk that the mental health impact of Covid-19 will be more than the physical effects of the virus. This, coupled with the expected huge increase in IAPT referrals, means we are seeing a very worrying trend.

“Patient referral rates have been alarmingly low since lockdown across IAPT services in England. In London alone we have seen up to a 50% reduction in referrals in March and April,” he added.

NHS England dismissed Ieso’s analysis as “a back of the envelope calculation that relies on implausible assumptions and guesswork, which will almost certainly not turn out that way.

“No one is anticipating three months’ worth of referrals materialising in a single month, and referrals are already starting to catch-up with pre-Covid-19 levels, so it is simply wrong to state that they will stay down at the end of September and create a big backlog.”

A spokesperson stressed that services to help people with stress and anxiety have been available throughout the pandemic and that referrals have started to rise again recently.

Fears over a looming mental health crisis have also been raised in schools, with less than 5% of teachers expressing confidence that they will be able to effectively support an influx of vulnerable and traumatised pupils in September, according to research by the Chartered College of Teaching, the official professional body for the teaching profession.

Teachers reported that during the crisis, they were dealing with issues including domestic violence, death of students’ parents and grandparents and suicide, as well as needing to direct families to foodbanks and charities for support. In many cases, they said they felt isolated and ill-equipped to provide this advice.

The study also found that a third of teachers think the crisis has negatively affected the wellbeing of most or all of their students, while 98% thought at least some of their students had been affected by partial school closures and lockdown measures.

Clear concerns emerged for pupils with mental health issues, those living in poverty, students with special educational needs and those without internet access. Around 40 per cent are planning specific support for bereaved or traumatised students. The concerns are already shaping the response to a wider reopening of schools in September. More than half of teachers said their schools were considering how to help children make transitions to new classes, with 44% discussing curriculum changes.

The discussions with teachers revealed that school staff largely want to prioritise wellbeing and rebuilding relationships with students, preferring to allow more time for re-establishing friendships, talking about their experiences and doing outdoor exercise.

Alison Peacock, chief executive of the Chartered College of Teaching, said the findings painted “a worrying picture of the education landscape”. She added: “The level of anxiety about pupils’ learning and wellbeing is deeply concerning.”