The Role of Defense Mechanisms in Self-Injurious Behaviors: A Systematic Review

The identification of psychological risk factors for suicide and self-harm behaviors is necessary for preventive and therapeutic strategies. The aim of this article is to systematically review research articles concerning the relationship between defense mechanisms and self-injurious behaviors according to PRISMA criteria.

PubMed, Web of Science, PsycInfo, and Scopus electronic databases were searched from inception to 01/27/2025 by combining the keywords "defense mechanism*" AND "suicid*" OR "non suicidal" OR "self harm" OR "self injury." Risk of bias was examined with the Study Quality Assessment Tools of the National Heart, Lung, and Blood Institute.

A total of 428 records was yielded by electronic search and after removal of duplicates and application of inclusion criteria 24 articles fulfilled the inclusion criteria. Six additional articles were added by means of references search, leading to a total of 30 included articles. About half of the studies were performed in adult samples and the remaining in children and adolescents. Most of the articles included patients recruited in psychiatric settings. Both in adults and adolescents, a significant association between immature defenses, especially displacement, splitting, acting out, and projection, and increased risk for self-injurious behavior was found. Conversely, mature defenses were inversely associated with self-harm ideation and behaviors.

Defenses represent an area where early intervention could be implemented as part of a preventive strategy to reduce self-injurious behaviors. A routine evaluation of defensive functioning should be methodically included in the psychological assessment of patients with self-harming ideation or behaviors.