Patterns of salivary cortisol secretion and responses to daily events in patients with remitted bipolar disorder

Previous studies on bipolar disorder revealed abnormalities in the function of the HPA axis, including disturbed patterns of cortisol secretion, during depressive and manic episodes. It is less clear whether these abnormalities persist after symptomatic recovery. In the present study we used the experience sampling method with intensive salivary cortisol sampling to study patterns of cortisol secretion in relation to negative and positive daily events during the normal daily life of a group of 36 patients with remitted bipolar disorder and 38 healthy controls. Results of multilevel regression analysis indicated that daytime cortisol levels and reactivity to daily events were similar in remitted bipolar patients and healthy controls, but bipolar patients showed flatter diurnal slopes and larger cortisol fluctuations over successive measures. Patients with many previous episodes had higher overall cortisol levels, reduced cortisol reactivity to negative daily events, and flatter diurnal slopes than patients with fewer episodes. These results provide additional evidence of subtle HPA axis dysregulation in remitted bipolar patients, especially in those with many recurrent episodes.