UN investigators said last week that the Islamic State of Iraq and Syria (ISIS) is committing crimes against humanity in Syria, including beheading boys as young as 15 and using child soldiers.
Syrian children have also been abducted by ISIS, as in May when the group kidnapped 153 Kurdish Syrian students aged 13 to 16 near Manbij village as they returned home to Kobani from Aleppo, where they had taken year-ending middle school certificate exams.
By October, all children had been released after activists launched humanitarian campaigns at every level calling for their return.
Farhad Shaheen, 15, said that throughout his four months in captivity, he was subjected to torture and daily attempts by the group to instil its doctrine in his mind.
His brother was able to guide him back to the views on which he was raised, he said. ISIS attempted to brainwash him and fill his mind with dark views.
"I cannot forget the period I spent in ISIS captivity, where I spent four months and six days, all of which felt the same," Farhad told Khabar.
He said he was detained with the other children in a Syrian school under ISIS control.
The abducted children spent their days reading the Qur'an, attending religious classes, praying and listening to religious lectures that said all Syrian revolutionary groups are infidels, Farhad said.
At times, some of the children were beaten for disobeying gunmen's instructions or for refusing to accept their views, he added.
Once, Shaheen said, he attempted to escape with two other children. They were caught and "subjected to severe punishment, including imprisonment in the rooms and beatings". He did not believe it when told he was being released because gunmen had previously told some abductees the same story and did not release them.
Shaheen said he hopes to return to school but the circumstances of his displacement to Turkey could prevent him from doing so.
Mohammed Shaheen, Farhad's brother, told Khabar he noticed a change in his brother's behaviour, speech and state of mind upon returning from captivity.
Since then, Mohammed said, he has been trying to return his brother to the mental state he was in before his capture.
So far, he said, he has been able to purge some of the views the ISIS gunmen had tried to plant in Farhad's mind, "especially in relation to takfiri [ideology]".
Children returning from captivity require special care, Shaheen said, noting that he was able to treat his brother because he is a teacher and capable of handling such special cases.
Other families could face a bigger problem if the "dark views" planted in their children's minds remain, he said.
The majority of the children who were released are natives of Kobani and the surrounding villages, he said. Many are now dispersed because of the battles against ISIS there and the on-going displacement, making it difficult to follow up on them.
However, a number of activists have "launched campaigns on social networking sites, Facebook in particular, to follow up on news relating to the captive students", said Mohammed.
He added now that Syrian Kurdish students have been released, activists shifted their attention to calling for the release of other civilians abducted by ISIS but who remain unaccounted for.
Child psychologist and Ain Shams University lecturer Enas al-Jamal said it is crucial that freed children undergo psychiatric and social therapy sessions.
Such therapy could be conducted for two reasons, she said: treating the negative effects of the kidnapping on the children's psyches and extracting the dark views planted in their minds during so-called religious lessons, "often persuasive to children".
Parents and the children's post-release environment in the first few months after release also are crucial, she said, urging normal family relationships, affection and care.