BackgroundPatients with major depression and borderline personality disorder arecharacterised by a distorted perception of other people's intentions.Deficits in mental state decoding are thought to be the underlying causeof this clinical feature.AimsTo examine, using meta-analysis, whether mental state decoding abilitiesin patients with major depression and borderline personality disorderdiffer from those of healthy controls.MethodA systematic review of 13 cross-sectional studies comparing Reading inthe Mind of the Eyes Test (RMET) accuracy performance of patients withmajor depression or borderline personality disorder and healthyage-matched controls (n = 976). Valence scores, wherereported, were also assessed.ResultsLarge significant deficits were seen for global RMET performance inpatients with major depression (d =–0.751). The positiveRMET valence scores of patients with depression were significantly worse;patients with borderline personality disorder had worse neutral scores.Both groups were worse than controls. Moderator analysis revealed thatindividuals with comorbid borderline personality disorder and majordepression did better than those with borderline personality disorderalone on accuracy. Those with comorbid borderline personality disorderand any cluster B or C personality disorder did worse than borderlinepersonality disorder alone. Individuals with both borderline personalitydisorder and major depression performed better then those with borderlinepersonality disorder without major depression for positive valence.ConclusionsThese findings highlight the relevance of RMET performance in patientswith borderline personality disorder and major depression, and theimportance of considering comorbidity in future analysis.