Understanding Radicalisation: A Review of the Quality of Psychological Evidence Behind Violent Extremism

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Violent extremism remains a pressing concern for prevention professionals across sectors, yet our understanding of how individuals become radicalised is still evolving. Our recent systematic literature review by Henrich, Ireland, and Lewis provides a comprehensive synthesis of all available research into the psychological processes behind radicalisation. Reviewing 96 empirical studies, this work offers valuable insights which can inform policy, frontline practice, and future research across both community and forensic settings.

The review identifies eight core themes influencing radicalisation. These range from extremist attitudes and social influences to mental health concerns and personal grievances. Notably, the most empirically supported factors included prior violent behaviour, exposure to radicalised peer groups, and the legitimising role of ideology and group identity. However, the evidence surrounding mental health and sociodemographic characteristics, often assumed to be predictors, was inconclusive or contradictory.

Crucially, the review highlights the overlap between risk factors for general violence and those for extremist violence. This raises questions about the specificity of existing prevention tools and calls for a more nuanced, individualised approach. While ideology and beliefs are often associated with radicalisation, they are not always necessary or sufficient causes. Instead, the interaction of personal vulnerabilities, social pressures, and identity dynamics appears more relevant in many cases.

Underexplored areas, such as the radicalisation of individuals in forensic mental health settings, such as prisons or psychiatric settings, or those with complex psychiatric needs, remain significant gaps in the literature. Only five studies specifically examined populations in these settings, despite concerns that such environments can act as either catalysts or disruptors to radicalisation.

• Risk factors for violent extremism often mirror those for general violence, such as a history of aggression or exposure to delinquent peers.
• Ideology, while frequently studied, is not a consistent predictor.
• Protective factors, like prosocial engagement or critical thinking, are understudied but potentially powerful.
• Forensic settings are underrepresented in research, even though they may offer unique opportunities for intervention.
• Prevention efforts must consider the individual, not just the ideology, and adapt tools accordingly.

This literature review reinforces the need for an interdisciplinary, evidence-based approach to preventing violent extremism. For professionals working in education, healthcare, social work, and the justice system, the findings underline the importance of considering broader behavioural and social factors rather than relying on demographic profiles or ideological markers. As the field progresses, investing in research that explores underrepresented groups, and protective pathways will be essential to designing effective, inclusive prevention strategies.

Suggested links:
Radicalisation across the community and forensic units: a systematic literature review on the psychology of violent extremism
Risk and protective factors in risk assessment: Predicting inpatient aggression in adult males detained in a forensic mental health setting

Author: Dr Sören Henrich, lecturer and published scholar in Forensic Psychology for the Manchester Metropolitan University, UK. He has more than a decade of clinical experience working with extremely violent individuals with complex mental health issues, both in Germany and the UK. Dr Henrich delivers international training on risk and threat assessment and remains a clinical advisor for secure forensic settings in England.