Rumination, co-rumination and latent trait cortisol (LTC): the moderating role of depression history.

Although research has linked rumination to various hypothalamic-pituitary-adrenal (HPA) axis indicators, few studies have examined whether rumination - and its interpersonal counterpart, co-rumination - is uniquely associated with trait-like individual differences in HPA axis activity. The present study tested whether rumination and co-rumination were related to latent trait cortisol (LTC), a trait-like marker of individual differences in HPA axis activity, and whether these associations were moderated by current and lifetime histories of depressive symptoms. Undergraduates (N = 85; M age = 19.37 years) provided salivary cortisol samples four times daily (waking, 30 and 45 min post-waking, bedtime) over three 3-day sampling waves separated by 6 weeks. Rumination and co-rumination were assessed via self-report, and current and lifetime history of depressive symptoms via semi-structured interviews. An across-wave LTC was derived using the first two morning samples from nine collection days. Greater rumination and co-rumination were associated with lower across-wave LTC among individuals without a history of diagnosable depression. These results suggest that intrapersonal and interpersonal emotion regulation strategies are associated with individual differences in HPA axis activity primarily among those without a depressive history. This work provides novel insight into a potential physiological pathway through which rumination and co-rumination may shape the risk for the first onsets of depression.