Defenses are theorized to develop within early caregiving relationships, yet no meta-analysis has quantified their association with childhood maltreatment. This PRISMA 2020-guided meta-analysis, which was not preregistered, addressed this gap for Overall Defensive Functioning (ODF) and immature, neurotic, and mature defenses. We searched PsycINFO, PubMed, Web of Science, and ProQuest Dissertations & Theses Global through August 20, 2026. Eligible studies quantified maltreatment before age 18 and ODF or defense categories, excluding studies using only dichotomous maltreatment indicators or broad trauma inventories underrepresenting maltreatment. We rated study quality with an adapted NIH Quality Assessment Tool. Random-effects models pooled Fisher’s z, back-transformed to r; meta-regression and subgroup analyses tested moderators. We included 35 cross-sectional studies (34 independent samples; N = 13,604). Greater maltreatment was associated with lower ODF (k = 7; r = −.17, 95% CI [−.20, −.13]) and greater reliance on immature (k = 30; r = .24, 95% CI [.18, .29]) and neurotic defenses (k = 21; r = .12, 95% CI [.06, .19]), whereas the mature-defense association was negligible (k = 24; r = −.04, 95% CI [−.09, .01]). Heterogeneity was substantial for defense categories but not ODF; publication bias was not evident. Exploratory moderator analyses suggested variation by maltreatment instrument and sex composition (immature), sample type (neurotic), and defense instrument (mature). Cross-sectional, retrospective evidence precludes causal inference. Findings are consistent with psychodynamic and developmental models in which childhood maltreatment shifts defensive organization toward less adaptive modes without precluding mature defenses; prospective longitudinal studies should test this proposition.
