The problem is particularly severe for girls who fall victim to cruel remarks about their appearance and weight.
Figures from the Priory Group, the country’s largest organisation for mental health hospitals and clinics, show admissions for anxiety in teenagers has risen by 50 percent in only four years. In 2014 a total of 262 girls and boys aged 12 to 17 were admitted to one of its centres with severe depression or anxiety, up from 178 in 2010.
But this is almost certainly an underestimate because there are hundreds of others on waiting lists who have been referred by GPs but not yet seen by a specialist.
Separate figures from the Office for National Statistics show that a fifth of teenagers and young adults suffered some degree of depression and anxiety last year, a higher proportion than in other generations.
Psychiatrists blame sexting, in which youngsters text explicit photos of themselves to friends who then comment. They say some see it as a “form of courtship” and the chance to be noticed by the opposite sex. But the photos can provoke extremely unkind comments, particularly if unflattering images of someone are sent round behind their backs.
They are also worried about online bullying on websites such as Facebook, Twitter and Ask.Fm – often by anonymous ‘trolls’ they have never met.
In 2012 and 2013 the Ask.fm website was directly blamed for the deaths of four teenagers in England and Ireland. These included Hannah Smith, who hanged herself aged 14 after months of taunting by anonymous users over her weight, the death of an uncle and her self-harming.
Hannah, from Lutterworth, Leicestershire, received messages telling her she was an “ugly ******” and a “fat s***”. Less than a fortnight before her body was found in 2013, she had begged her tormentors to stop.
Ask.fm encourages its 60 million users worldwide to ask a question which is then answered by everyone else, anonymously. Teens often post pictures of themselves and these can provoke spiteful comments.
Dr Natasha Bijlani, consultant psychiatrist at the Priory Hospital Roehampton, South-West London, said: “This relatively new phenomenon of sexting – where explicit texts and pictures are sent between smartphone devices – seems to have become endemic, and we are not sure of the long-term consequences. However, coupled with online bullying, we can expect an increasing number of people suffering issues of trust, shame, and self-loathing, sometimes manifesting itself in self-harming.”
She said sexting was now seen as the “new courtship” but often had “nightmare consequences”.
“The long-term effects of bullying can be prolonged and pervasive,” she added. “Much more focus needs to be given to how best to educate young people about the risks of sending compromising images, and communicating with unknown others online, and how to cope with bullying via devices at school.
“Episodes in childhood are often repressed and only later in life do these issues surface in the form of depression, stress and anxiety and other serious psychological conditions.”
Jenny Edwards, chief executive of the Mental Health Foundation charity, said: “There is a need for schools to lead on promoting emotional wellbeing. We know that over half of adults with serious mental health problems were first diagnosed when children.
“But we need to recognise that while new technology may increase stress in some circumstances, it can also reduce it by creating online support and increasing access to treatment.”