Currently the Dutch government funds dozens of social interventions designed to tackle polarization and radicalization issues. It is still unknown whether the assumptions underlying these interventions are valid. This article puts the theories of change of such interventions to the test. Underlying causal assumptions of four dominant Dutch social policies were confronted with scientific evidence: (1) the system-based approach, (2) peer mediation, (3) intergroup contact and (4) self-esteem enhancement. System-based approaches – comparable to multi-systemic therapy (MST) – seem effective in reducing extremist behaviour in radical youth, but do not necessarily lead to an ideological change. In peer mediation, the causal link between the deployment of young people and the positive outcomes of such methods remains unclear. Peer mediation is also more likely to contribute in conflicts that have not yet escalated. Intergroup contact reduces prejudices about other groups, but has a limited effect. There is also no evidence for a long term effect and positive outcomes of intergroup contact do not automatically apply to adolescents. Finally, it is questionable that enhancing the self-esteem of (moslim) youth makes them more resilient against radical tendencies. In the same vein, the scientific evidence is ambiguous about whether increasing self-esteem results in social desirable behaviour or improved social relations.