1) Buckley T, Schatzberg Z. On the interactions of the hypothalamic-pituitaryadrenal (HPA) axis and sleep: normal HPA axis activity and circadian rhythm, exemplary sleep disorders. J Clin Endocrinol Metab. 2005; 90(5):3106-3114.
2) van Liempt, S., Adrends, J., Cluitmans, PJ., Westenberg, HG., Kahn, RS., Vermetten, E. (2013, Jan). Sympathetic activity and hypothalamo-pituitary-adrenal axis activity during sleep in post-traumatic stress disorder: a study assessing polysomnopraphy with simultaneous blood sampling. Psychoneuroendocrinology, 38(1): 155-65.