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

Introduction: 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: Following PRISMA 2020 guidelines, we searched PubMed/Web of Science/(EBSCO)PsycINFO until 13/04/2023 for studies assessing defense mechanisms with measures based on the hierarchical model in patients with depressive disorders compared to non-clinical controls or throughout psychological intervention. We examined mature defenses/non-mature (neurotic/immature) defenses/overall defensive functioning (ODF) conducting random-effect meta-analyses with standardized mean difference (SMD) as the outcome measure metric. We also performed meta-regression/sub-group/sensitivity analyses. Study quality was appraised using the Newcastle-Ottawa Scale (NOS) and GRADE (Grading of Recommendations, Assessment, Development and Evaluations) was employed to assess the certainty of evidence for aim b outcomes. Results: 18 studies were included (mean NOS score = 5.56). Our findings show that depressive individuals used significantly more non-mature defenses than non-clinical controls (SMD = 0.74; k = 13) while non-clinical controls did not significantly differ in the use of mature defenses compared to depressive patients (SMD = 0.33; k = 14). Significant moderators included publication year/NOS score/geographical distribution/mean age for non-mature defenses, and NOS score/geographical distribution for mature defenses. Finally, only ODF showed a significant increase throughout psychological interventions (SMD = 0.55; k = 2) (GRADE=very low). Discussion: 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. However, the quality of many studies was medium/sub-optimal, and longitudinal studies were scarce, underscoring the need for further research.