According to an American study, 85 million files on child abuse were spread in 2021 - an increase of 30 percent from 2020. But Christoffer Rahm says that it can take decades before people with a sexual interest in children, or pedophile disorder, commit crimes or are detected by society in other ways way.

- It can be a matter of life and death in many cases, so we really wanted to test the treatment before it is widely recommended, he says.

But reaching out to the group is complex and many are too ashamed to seek care themselves.

Therefore, it was decided to recruit in online perpetrator forums – in this case on the encrypted part of the internet, better known as the darknet.

Was offered CBT treatment

The treatment was given in English and people from all over the world could participate anonymously.

The majority of people in the study had no criminal record and about half were between 18 and 30 years old.

Half of the participants underwent a placebo treatment while the other group underwent the active CBT treatment.

In the video: See how the researchers went about it and hear about the results.

The study has attracted international interest and Karolinska Institutet has already started the follow-up study, with updated treatment.