Systematic review: Risk factors and mechanisms of radicalization in lone-actor grievance-fueled violence

Abstract

The purpose of this systematic review is to identify risk factors and mechanisms of radicalization associated with lone-actor grievance-fueled violence. In this paper, I focus on five violent lone-actor “types”; lone-actor terrorists, workplace attackers, school shooters, rampage shooters and violent Incels. Data synthesis of the 78 included studies led to the identification of nine risk factors: 1) sociodemographic background; 2) social ties; 3) interpersonal rejection; 4) mental illness; 5) subclinical personality traits; 6) strain; 7) grievances; 8) emotional traits and states; and 9) cognitive processes and content. As a limitation of the extant literature is the lack of a coherent and integrative framework of how each factor relates to the others, findings were re-synthesized to show how risk factors essentially reflect five generic social and psychological mechanisms of radicalization: socialization, small-group dynamics, psychological need restoration, mental health from a dimensional perspective, and mechanisms of moral disengagement. The paper ends with a discussion of this framework and its implications for future research on lone-actor grievance-fueled violence.

KEYWORDS:

• Lone-actor grievance-fueled violence
• radicalization
• risk factors
• systematic review

Acknowledgements

I am deeply grateful to Preben Bertelsen (Department of Psychology and Behavioral Sciences, Aarhus University) and Oluf Gøtzsche-Astrup (Department of Political Science, Aarhus University) for their advice and commentary of this paper. I am also very thankful to PhD Candidate Patrick Cairns (Department of Psychology and Behavioral Sciences, Aarhus University) for his helpful comments, and to Cecilie Bogner for proofreading the entire manuscript. At last, I would like to thank all experts in the field who contributed to the grey literature search.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Notes

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