Defensive functioning in individuals with depressive disorders: A systematic review and meta-analysis

Background: This systematic review and meta-analysis aimed to address the limited generalizability of studies on defense mechanisms in depression by comparing depressive individuals with non-clinical controls (aim a) and examining changes throughout psychological interventions (aim b) (PROSPERO CRD42023442620). Methods: We followed PRISMA 2020 guidelines, searching PubMed/Web of Science/(EBSCO)PsycINFO until 13/04/2023 for studies evaluating defense mechanisms with measures based on the hierarchical model in depressive patients versus non-clinical controls or throughout psychological intervention. We conducted random-effect meta-analyses for mature defenses/non-mature (neurotic/immature) defenses/overall defensive functioning (ODF), with standardized mean difference (SMD) as outcome measure metric. Meta-regression/sub-group/sensitivity analyses were conducted. Study quality was appraised using the Newcastle-Ottawa Scale (NOS), and certainty of evidence for aim b outcomes was evaluated using GRADE (Grading of Recommendations, Assessment, Development and Evaluations). Results: 18 studies were included (mean NOS score = 5.56). Depressive patients used significantly more nonmature defenses than non-clinical controls (SMD = 0.74; k = 13). Non-clinical controls did not significantly differ in use of mature defenses compared to depressive patients (SMD = 0.33; k = 14). Significant moderators were publication year/NOS score/geographical distribution/mean age for non-mature defenses and NOS score/geographical distribution for mature defenses. Throughout psychological interventions, only ODF significantly increased (SMD = 0.55; k = 2) (GRADE = very low). Limitations: Quality of many studies was medium/sub-optimal, and longitudinal studies were scarce. Conclusion: Individuals with depressive disorders show a high use of non-mature defenses that could be assessed and targeted in psychological interventions, especially in younger patients.