Date on Master's Thesis/Doctoral Dissertation


Document Type

Doctoral Dissertation

Degree Name

Ph. D.


Psychological and Brain Sciences

Committee Chair

Sephton, Sandra E.

Author's Keywords

Circadian rhythms; Psycho-oncology; Actigraphy; Breast cancer; Intrusions


Circadian rhythms; Breast--Cancer--Patients


Cancer patients show circadian disruption that increases as disease progresses. Disrupted endocrine and activity rhythms predict early metastatic cancer mortality. Effects of psychological versus biological factors on rhythms are unknown, as are potential links between endocrine and sleep disruption, and relevance of disruption in early stage cancer. This study sought to examine the associations of cancer-related intrusions and avoidant coping with circadian cortisol rhythms, assessed with saliva samples, and rest/activity rhythms, assessed with actigraphy. Participants were women who had been recently diagnosed with breast cancer, meaning participants provided data at similar points in the course of diagnosis and treatment of cancer. Between diagnosis and surgical treatment, 45 women with breast cancer completed four days of data collection including daily reports on intrusions (IES intrusion scale) and avoidant coping (Brief COPE avoidant coping subscales), 12 saliva samples (waking, +30 minutes, 16:00 hours, bedtime), and actigraphy recordings. Mean intrusion and avoidant coping scores were calculated. Cortisol EIA assay results were examined for outliers and log-transformed prior to calculation of the diurnal slope. Actigraphy yielded the activity rhythm (autocorrelation coefficient), activity while in bed and out of bed (dichotomy index), and sleep variables. This study was unique in its opportunity to explore circadian disruption through collection of multiple measures of circadian rhythmicity and daily reports of breast cancer-related intrusions and avoidant coping while patients adjusted to diagnosis and anticipated treatment. Hierarchal regression analyses adjusted for relevant demographic and medical variables. Intrusions and avoidant coping were independently related to activity rhythm disruption (R2 change = .146 and .098, p = .008 and .034, respectively). Avoidant coping was associated with higher activity while in bed (R2 change = .168, p = .006). Circadian rhythm measures, diurnal cortisol slope and autocorrelation, were significantly associated in the predicted direction (r = -.613, p < .001). Higher autocorrelation was related to higher waking, and lower bedtime cortisol (r = -.459, p = .003). Breast cancer-related intrusions and avoidant coping may influence circadian rest/activity with possible implications for clinical intervention.