The goal of this prospective multicentred, stratified, parallel-group superiority study is to prevent and reduce the usage of Child Sexual Abuse Material (CSAM) by a Therapist Chat Service (TCS) and Selfhelp Platform for Self-Referred Patients, mostly men with a sexual interest in children. The interventions are based on Cognitive Behavioral Therapy (CBT) principles and designed to treat the sexual behavioral disorder related with CSAM consumption.

1. Participants in the Selfhelp modules group will show a statistically significantly higher proportion of reduction in CSAM behaviours four weeks after baseline, as compared to participants in the waitlist control group.
2. Participants in the Selfhelp modules followed by TCS group will show a statistically significantly higher reduction of CSAM behaviours compared to participants in the Selfhelp-only and TCS-only groups, post-intervention.

Researchers will compare TCS-only-, Selfhelp-only-, Selfhelp + TCS- and Waiting group to see if if the interventions decrease CSAM use and improve mental well-being.

Participants will get web based selfhelp-modules and/or text-based chat intervention operated by trained therapists.

The study will evaluate whether the TCS intervention and Selfhelp modules, independently or combined, effectively reduce CSAM use or risk of CSAM consumption and improve mental well-being among self-referred participants.

1. Objectives 1.1 Primary objectives

1. To compare the effectiveness in reducing CSAM behaviours between the TD only group and the waitlist group four weeks after the baseline assessment.
2. To compare the post-intervention effectiveness in reducing CSAM behaviours of the Selfhelp modules versus TCS alone and Selfhelp modules followed by TCS.

1.2 Secondary objectives

1. To assess the reduction in severity, time and self-rated risk of CSAM consumption among participants in the intervention groups (Selfhelp modules, TCS, or Selfhelp + TCS) compared to the waitlist control group, at post-intervention.
2. To compare the impact of the interventions (Selfhelp modules, TCS, or Selfhelp + TCS) on mental wellbeing, in contrast to the control group, at the end of the intervention period.
3. To evaluate the effect of the interventions (Selfhelp modules, TCS, or Selfhelp + TCS) on total sexual outlet compared with the waitlist control group after the intervention period.
4. To identify any adverse effects associated with the interventions (Selfhelp modules, TCS, or Selfhelp + TCS).

2. Hypotheses

2.1 Primary hypothesis

1. Participants in the Selfhelp-only modules group will show a statistically significantly higher proportion of reduction in CSAM behaviours four weeks after baseline, as compared to participants in the waitlist control group.
2. Participants in the Selfhelp modules followed by TCS group will show a statistically significantly higher reduction of CSAM behaviours compared to participants in the Selfhelp-only and TCS-only groups, post-intervention.

2.2 Secondary hypothesis

1. Participants in the intervention groups (Selfhelp modules, TCS, or Selfhelp + TCS) will show a statistically significant reduction in the severity, time and self-rated risk of CSAM consumption compared to participants in the waitlist control group, four weeks after the initial intervention. Among the intervention groups, it is expected that the Selfhalp + TCS group will show the greatest reduction in CSAM consumption, followed by the TCS group and then the Selfhelp-only group.
2. Participants in the intervention groups (Selfhelp modules, TCS, or Selfhelp + TCS) will show a statistically significant improvement in their mental well-being (measured using the Warwick-Edinburgh Mental Wellbeing scale). compared to participants in the waitlist control group, at post-intervention. Among the intervention groups, the Selfhelp + TCS group is expected to show the greatest improvement, followed by the TCS group, and then the Selfhelp-only group.
3. Participants in the intervention groups (Selfhelp modules, TCS, or Selfhelp + TCS) will show a statistically significant reduction in total sexual outlet (measured using a self-reported measure) compared to participants in the waitlist control group, after the intervention. Among the intervention groups, the Selfhelp + TCS group is expected to show the greatest reduction, followed by the TCS group, and then the Selfhelp-only group.
4. All intervention groups (Selfhelp modules, TCS, or Selfhelp + TCS) will experience adverse effects (psychological and emotional distress) to a similar extent, with no significant differences in the number or type of adverse effects reported. Adverse effects are expected to primarily involve mild to moderate psychological and emotional distress, such as feelings of anxiety or frustration, but are not expected to lead to severe distress or long-term harm.

3.Trial design

This is a prospective, randomised, multicentre, open-label, parallel-group, superiority trial designed to compare stratified, pair-matched CSAM users across three intervention groups and one wait-list control group, with an allocation ratio of 1:1:1:1. Following participant agreement to the terms of the study, demographic information, measures for stratified randomization, and baseline outcome data will be collected. Additionally, data collected from the four groups Selfhelp modules, TCS, Selfhelp + TCS, and waitlist) of the TD-CHAT study will be compared with data from a fifth group (waitlist + TCS) sourced from the "Scalable Technology for Online Prevention of Child Sexual Abuse and Child Sexual Abuse Materials" (STOP-CSAM) project.

Inclusion Criteria:

• Adult participant (≥18 years);
• recent (last 2 weeks) CSAM use or past CSAM use and self-reported risk;
• proficiency in English, German or Spanish;
• voluntary participation and agreement to the terms of the study.

Exclusion Criteria:

• Severe neuropsychiatric comorbidities (unstable psychotic disorder, organic brain damage, diminished intellectual functioning, untreated drug or alcohol addiction);
• history of contact CSA perpetration (past or present);
• ongoing criminal investigation, trial, punishment, or probation status for online or offline CSA or CSAM use;
• current inpatient psychiatric treatment or other concurrent treatment targeting CSAM behaviours