Attachment Styles in Major Depressive Disorder: A Systematic Review and Meta-Analysis.

Major depressive disorder (MDD), a leading cause of disability, is associated with difficulties in close relationships. Attachment theory links early caregiving to internal working models shaping emotion regulation, interpersonal functioning and depression vulnerability. Attachment patterns in clinically diagnosed MDD have not been synthesised. Following PRISMA (PROSPERO: CRD42017068580), we searched for studies of adults with standardised diagnoses of MDD or postpartum depression (PPD) and attachment measures. Random-effects meta-analyses expressed categorical outcomes as odds ratios (ORs) and continuous outcomes as Hedges' g. As a result, 61 studies met inclusion criteria: 33 case-control and 28 depression-only, of which five provided qualitative data only. Categorically, MDD/PPD showed lower secure (OR = 0.20, 95% CI 0.15-0.26, p < 0.001) and higher anxious (OR = 2.46, 1.66-3.64, p < 0.001), avoidant (OR = 1.42, 1.04-1.95, p = 0.027) and fearful attachment (OR = 3.00, 1.97-4.54, p < 0.001) than healthy controls. On continuous measures, secure attachment was lower (g = -0.46, p = 0.003) and anxious (g = 0.63, p < 0.001) and avoidant (g = 0.41, p = 0.011) higher; fearful was not significant (g = 0.35, p = 0.062) until an outlier was removed. Single-arm prevalence meta-analyses found secure attachment in 24.1%, fearful in 26.9%, avoidant in 23.7% and anxious in 23.0%, with secure more prevalent in PPD than MDD (31.9% versus 21.3%, p = 0.009). In conclusion, MDD and PPD show lower secure and higher anxious, fearful and avoidant attachment than healthy controls. About three in four patients show insecure attachment, supporting attachment-informed assessment and treatment planning.