According to GP records, the Covid pandemic coincided with a sharp increase in eating disorders and self-harm among teenage girls in the UK.
The increases were greatest among girls living in the wealthiest areas, which could be due to better GP access.
Young women have told the BBC that a behavioral trigger for them during lockdown was feeling like they had no control over their lives.
The government says it is investing in eating disorders services to help more children and young people.
Regardless of location, charities assert that everyone needs access to early assistance for mental health issues.
19-year-old Annabelle from Surrey recalls how challenging lockdown was.
"We had very little control over our lives; our GCSE exams were postponed, and we had no say in the final grades.
We were unable to control our movement and couldn't see people.
"The only factors we had any control over were your diet and appearance, so I decided to pay attention to those. ".
Annabelle overcame her bulimia with help, and while she is now feeling better, her family is still footing the bill for her private therapy.
People don't realize how prevalent eating disorders are, according to her, because "I don't know a single girl or female friend who hasn't had some sort of struggle with eating.". ".
"It's incredibly hard, but there isn't enough help for everyone on the NHS.
Sophie Rowland, 18, from South Shields, has been posting about her recovery from anorexia on TikTok.
Before the pandemic, she was a huge food lover, but being cooped up inside during the lockdown made her become obsessed with working out and watching workout videos online.
"I've just realized I can't stop keeping track of calories.
"Everything was just food, food, food - and it was food that became the enemy. ".
She told her mum one day, and says she was "very lucky" with the help she received from nurses, friends and family.
Positive feedback from her videos have also aided her recovery and now she wants to help others.
Eating disorders and self-harming have been rising among children and young people for a number of years but "increased substantially" between 2020 and 2022, the study found.
Over that period, around 2,700 diagnoses of eating disorders were anticipated among 13-16-year-olds, but 3,862 were actually observed - 42 percent more than the expected figure.
In the same age group, 6,631 cases of self-harm were expected but 9,174 were recorded by GPs - 38 percent more than predicted.
Among 17-19-year-olds eating disorders also rose above expectations.
The analysis, by the University of Manchester, Keele University and University of Exeter, looked at nine million records belonging to patients aged 10-24 years, from nearly 2,000 GP practices across the UK.
Dr Shruti Garg, from the University of Manchester - a child and adolescent psychiatrist and the study author - called it a "staggering rise" which highlighted an urgent need to improve early access to support.
An eating disorder - most commonly anorexia or bulimia - is a mental health condition where control over food is used as a means of coping with distress and other difficult situations.
During the pandemic, prolonged access to social media, more focus on body image and less face-to-face contact may have led to feelings of low self-esteem and psychological distress, particularly among adolescent girls, the study says.
Social media may also have exposed young people to content which increased the risk of developing an eating disorder.
In the media "there was a lot of emphasis on food availability and restriction, and also on the message that being overweight was a risk for Covid," Dr Garg notes.
The research also suggests young people might self-harm as a coping strategy in times of uncertainty.
Even before the pandemic, there had been a gradual decline in mental health generally among teenagers and young people - and a recent study found five children in every classroom had a probable mental disorder in 2022.
Since March 2020, GP records show a big rise in eating disorders among the richest in the UK population - with 52 percent of flagged eating disorders occurring in the least deprived areas and 22 percent in the most deprived.
Tom Quinn, director of external affairs at charity Beat, says there is still "a postcode lottery" for care and everyone needs to get "the help they need as quickly as possible".
"These figures are shocking but sadly not surprising," he adds.
"We also know that the NHS is treating more children and young people than ever before, with healthcare professionals under huge amounts of strain. " .
The study found no sign of increasing rates of eating disorders among boys or young men. Researchers say males have a higher suicide risk than females, suggesting mental health issues manifest in different ways.
The research, which was supported by mental health research charity The McPin Foundation, is published in the Lancet Child and Adolescent Health.
A spokesperson for the Department of Health and Social Care said they recognised "the devastating impact eating disorders can have on an individual and [their] family's life".
The government says it will invest an additional £2.3 billion a year in NHS mental health services by March 2024, alongside £54m a year to increase capacity at children and young people's community eating disorder services.
If you've been affected by the issues raised in this article, help and support is available via . BBC Action Line.
. It had taken over my life. "
