Dr Natasha Nijlani says a growing number of her adult patients have depressive or anxiety disorders linked to earlier online experiences.
Dr Nijlani says the consequences of that are “very worrying”.
“Things that happen to adolescents carry on emotionally to their early adulthood and I’m seeing the repercussions of cyber-bullying and online harassment with patients who are over the age of 18,” she says.
Dr Nijlani works for The Priory, which runs mental health rehabilitation services.
It has seen a rise of nearly 50% in four years of 12 to 17-year-olds admitted for serious depressive order, anxiety disorder and stress-related issues.
In 2014 there were 262 admissions, compared with 178 in 2010.
Dr Nijlani says the number of adult patients has grown in this time by 25%.
Although she says it’s good there is increased awareness of mental health issues and people seeking help, she’s also worried there’s a rise in the number of adults experiencing mental health problems.
She says in years to come there could be “an epidemic”, caused in part by “what happens online as teenagers”.
“Negative online experiences can lead to mental health problems if people are vulnerable.
“Social media makes it easier for bullies and gives us new ways of abusing each other.
“If you get bullied at that crucial stage in your development, when your character is being formed, there is good evidence it can affect your self esteem and confidence – and your whole life for many years,” she says.
“Sexting is often seen as harmless, but it can lead to shame and embarrassment.
“The permanence of life online mean it’s hard to move on – there are things you can’t delete.
“More people will be depressed in the future. In the past we didn’t have this record of our lives that is indelible.”
Last October the charity Ditch the Label found 37% of a group of just under 1,000 13 to 25-year olds had sent a naked photo of themselves to another person and 13% of them felt pressured into doing it.
The charity’s co-founder Dan Raisbeck says although awareness of the risks is growing amongst parents and teenagers, access to smart phones is also growing.
“Flirtatious messages online, are now seen as part of growing up and how you form relationships,” he says.
“When relationships break up we can see content that’s been sent online – ‘weaponised’ – with revenge porn and that kind of thing. It becomes extremely complex and damaging.”
Childline has seen an increase in cyber-bullying too. The charity says there’s been a 73% increase in counselling sessions about online abuse and safety between 2012 and 2014.
The charity launched an app called Zipit in October 2013 which helps children and teenagers deal with requests for explicit photos by giving them a series of joke images to send back.
It’s now been downloaded more than 60,000 times.
Supervisor Rosanne Pearce tells Newsbeat: “Cyber-bullying and sexting can cause great trauma for young girls in particular. We can’t change the fact we live in an online world – what we can do is support young people.”