Objective. Supportive close relationships are important for health. Mutuality, the reciprocal sharing of thoughts and feelings in close relationships, is linked with better outcomes for patients with rheumatoid arthritis (RA) in crosssectional data. Hypothesizing that mutuality has a beneficial impact on inflammation, we tested potentially causal relations of couple mutuality with erythrocyte sedimentation rate (ESR) in prospective data. Methods. Female patients with RA (n = 70; mean age 57 years, mean RA disease duration 5 years) completed questionnaires at baseline, 6 months, and 12 months, including measures of mutuality, RA flares, and negative affect. ESR laboratory values available near questionnaire dates were collected from medical charts. Using regression, we examined cross-lagged effects of mutuality and ESR over the two 6-month time spans (baseline to 6 months, 6 months to 12 months). We anticipated that mutuality would exert lagged inverse effects on subsequent ESR levels, and that ESR would have no effect on subsequent mutuality levels. Results. After controlling for lagged effects of earlier inflammation, disease-modifying antirheumatic drugs, antiinflammatory drugs, RA flares, and negative affect, mutuality's lagged inverse effects over both time spans accounted for unique variance in subsequent levels of ESR, explaining 9% at 6 months and 12.5% at 12 months. Concomitantly, earlier ESR had no effect on subsequent mutuality. Conclusion. Patients with RA reporting more mutuality had less inflammation at subsequent time points, but inflammation had no effect on subsequent reports of mutuality. This suggests that mutuality exerts a beneficial effect on inflammation. Clinical implications and potential applications are discussed.
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