Individual differences in emotional expressivity predict oxytocin responses to cortisol administration: Relevance to breast cancer?

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Reduced emotional expression has been consistently related to susceptibility or fast progression of breast cancer. Breast cancer development and reduced emotional expression have both been related to rejection- and separation-related conditions. The neuropeptide oxytocin is low in response to rejection or separation. Recent results suggest that oxytocin may protect against the development of breast cancer and slow its progression. In the present study, we investigated if individual differences in emotional expressivity relate to basal or cortisol-stimulated plasma oxytocin. Healthy female subjects were treated with placebo or 35 mg of cortisol orally in a double-blind within-subject study. Seventy minutes later, blood was sampled for determination of oxytocin and cortisol levels. We found an interaction between treatment condition and Emotional Expression-out scores: after cortisol treatment, oxytocin levels increased proportional to Emotion Expression-out score. These preliminary findings provide a potential mechanism for associations in the literature between emotional expressive behavior and breast cancer.