Psychological defense mechanisms as adaptive processes: A systematic review of theory and evidence

Psychological defense mechanisms constitute a foundational construct in understanding how individuals regulate internal conflicts, emotions, and threats to the self. Although originally formulated within classical psychoanalytic theory, contemporary research has increasingly reconceptualized defense mechanisms as adaptive, measurable, and developmentally organized processes that operate across clinical and nonclinical populations. The present article provides a comprehensive narrative review of empirical and theoretical studies on psychological defense mechanisms, with the aim of clarifying their conceptual evolution, empirical consolidation, and contextual relevance in modern psychological science.