High-achieving girls appear "particularly vulnerable" to Islamic radicalisation, a High Court judge has warned.
Mr Justice Hayden, who is based in the Family Division of the High Court in London, says he has analysed a number of cases where allegations of children being radicalised have been raised.
The judge says a pattern has emerged in relation to "recruitment to jihadist causes".
He has raised concerns in a ruling on a case involving a "perceptive and intelligent" girl in her mid-teens who was taken off a plane by police when heading for Syria.
Videos relating to Muslim extremism had been found at the girl's family home.
The girl had seen "numerous" videos which contained "violent and death-related images".
Mr Justice Hayden said the teenager had described "images" she had seen - and given "some of the most disturbing evidence I have ever heard".
The judge said the girl could not be identified.
He said social workers had asked him to make decisions about the youngster's future.
"I have now heard a number of cases concerning allegations of radicalisation of children," said Mr Justice Hayden in the ruling.
"In the cases that have come before me a pattern has emerged in which conscientious, hard-working and high-achieving young girls appear to be particularly vulnerable."
The judge said he had analysed the teenager's case at a private hearing in London earlier this year.
"(She) was asked about the number of videos she had seen which contained violent and death-related images," said the judge.
"She told me that they were too numerous to remember and that they no longer had any effect on her.
"Everybody in this courtroom will remember this piece of evidence. It was profoundly disturbing to listen to, not least because it was both uncompromisingly honest and manifestly accurate."
Mr Justice Hayden said he found the girl to be "intelligent and perceptive".
"As she described some of these images she became distant, withdrawn, flat and rather glazed in her expression," he said.
"She gave some of the most disturbing evidence I have ever heard from a child or, for that matter, an adult.
"She told me how violent beheadings, point-blank shootings through the brain and images of mass killings no longer had any impact upon her.
He added: "I am entirely satisfied that she was telling the truth about this. Her demeanour was entirely congruent with her verbal evidence. The impact of this evidence on all those who heard it will remain for a long time."
Mr Justice Hayden said "material" found at the girl's home had titles including: "A Muhajid's Guide to the West", "Hiding the extremist identity", "Miracles in Syria", "The Book of Jihad" and "44 ways to support jihad".
"My primary reason to go to Syria was to join an Islamic State," the girl had told Mr Justice Hayden.
"I believed that this was the best way for me to be a good Muslim.
"I believed that the West were responsible for the suffering of Muslims, particularly in Gaza, where innocent people and especially children were being bombed and killed.
"The UK was implicated in supplying arms.
"I felt a traitor living in the West.
She had added: "I believed that I might be able to study there, for free and that this would enable me to study to become a doctor, which, in turn, would enable me to help others. That was a very attractive promise that was made."
Mr Justice Hayden raised concerns about the girl's parents.
He said her father was "headstrong" and had made "absolutely no effort" to regulate his daughter's internet use.
"I do not believe that he had ever stopped to reflect on the extent to which his daughter could inflict emotional and psychological damage on herself by what she viewed on the internet," said the judge.
"(She) dehumanised herself by viewing a surfeit of death-related images that have left her emotionally numb.
"It is this that is the most striking feature of the case, more so than her reading the polemics or expressions of radicalised views."
But he said there was a "naivety" to her father's behaviour rather than a "deep-seated destructive agenda".
The judge said the girl's mother was "dedicated to a heightened code of Islamic belief".
"I do not find that the mother held radicalised beliefs but I have found that on a spectrum of Islamic observance she is at the most committed end," he added.
"In this family those beliefs proved to be fertile ground for (the teenager's) journey to radicalisation."
He concluded that the girl should live at home in future - but under the supervision of social services staff.
Social workers had plans which would give the girl "space" from her mother, said the judge.
The girl's father had "recognised the impact" that "death-related images" had on his daughter.
Police and social services staff would be vigilant in monitoring computer use.
And Mr Justice Hayden said the girl had the potential to "combat" her "addiction" to violent images.
The judge said the family lived in London.
He said Tower Hamlets Council had asked him to make welfare decisions.