Intimate Relationships and Depression: Searching for Causation in the Sea of Association.

This article provides a critical review of existing research on intimate (marriage or marriage-like) relationship distress and risk for depression. Using the meta-framework of research triangulation, we seek to synthesize research evidence across several different methodologies and study designs and to draw the most reliable conclusion regarding a potential causal association between relationship distress and depression. Focusing on existing correlational (i.e., observational), genetically informed, and intervention (i.e., experimental) research on the association between relationship distress and depression, we conclude that the existing body of research evidence supports the claim that relationship distress is a causal risk factor for depression. A secondary aim of the article is to highlight a variety of effective methods that, when viewed from the perspective of triangulation, enhance the pursuit of causal inference, including propensity score matching, target trial emulation, directed acyclic graph approach, and Mendelian randomization.