The mother of a London teenager who died after being hit by a train has urged every parent to be aware of the dangers of the internet.
St Pancras Coroner's Court was told Tallulah Wilson, 15, from West Hampstead, created a fantasy cocaine-taking character to escape reality.
In a statement, her mother Sarah said her daughter had been "in the clutches of a toxic digital world".
She added that in her final few weeks her family "could no longer reach her".
Sarah Wilson said that like any parent she had tried to protect her daughter, looking for help from professionals at her school and in the health sector.
"Our lives will never be the same without Tallulah," her statement said.
"We have lost someone more precious than words could ever say - a beautiful, loving and talented shining star has been stolen from our skies.
"Her sisters and I did everything we could to keep her safe, but she had fallen into a world of nightmares.
"She was in the clutches of a toxic digital world where in the final few weeks we could no longer reach her."
Tallulah Wilson died after being hit by a First Capital Connect train at St Pancras Station on 14 October, 2012.
The inquest heard how she posted self-harming pictures online.
In its narrative determination, the jury said that healthcare professionals and educators had a responsibility to "gain better understanding" of the importance of online life for young people after deciding that the teenager had taken her own life.
A statement said: "This case has highlighted the importance of online life for young people.
"We all have a responsibility to gain better understanding of this.
"This is a particular challenge for healthcare professionals and educators."
Sarah Wilson said she was "shocked by the ease with which Tallulah and other children could access online self-harm and suicide blogs".
She told the inquest that she had shut down her daughter's Tumblr account shortly before her death because it contained photos of her harming herself.
"Tallulah entered a world where the lines between fantasy and reality became blurred," she said. "It is every parent's worst nightmare.
"I appeal to big brands to withdraw their advertising from those sites who continue to host inappropriate self-harming and suicide-promoting blogs to stop this poison spreading.
"My family has suffered an irretrievable loss and would now appreciate some time to reflect and come to terms with a world eclipsed without Tallulah, but every parent needs to be aware of the dangers of the internet and what their children may be viewing online."
Anna Thwaites, the family's solicitor, from Hodge Jones & Allen LLP, said: "This is a tragic case. More needs to be done regarding the perils of the internet and the impact this has on our children."
A statement from Tumblr said: "Tallulah Wilson and her family are in the thoughts of Tumblr and its employees.
"Issues of depression and self-harm are extremely challenging, particularly in online environments that encourage self-expression.
"Tumblr has policies to address the most harmful of this content, and we have systems in place to direct users to appropriate resources for getting whatever help they may need.
"We are committed to continually improving our ability to act on self-harm content, and also to keeping Tumblr a positive, supportive environment for those individuals dealing with issues of depression and self-harm."
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