Symptom-system fit theory proposes that problematic behaviors are maintained by the social system (e.g., the couple relationship) in which they occur because they help promote positive relationship functioning in the short-term. Across three daily life studies, we examined whether mixed-gender couples reported more positive relationship functioning on days in which they engaged in more shared problematic behaviors. In two studies (Study 1: 82 couples who smoke; Study 2: 117 couples who are inactive), days of more shared problematic behavior were accompanied by higher daily closeness and relationship satisfaction. A third study with 79 couples post-stroke investigating unhealthy eating failed to provide evidence for symptom-system fit. In exploratory lagged analyses, we found more support for prior-day problematic behavior being associated with next-day daily relationship functioning than vice-versa. Together, findings point to the importance of a systems perspective when studying interpersonal dynamics that might be involved in the maintenance of problematic behaviors.
Keywords: couples; daily diary; problematic behaviors; relationship functioning; symptom-system fit.