The American Academy of Sleep Medicine defines sleep disturbance as "difficulty initiating sleep, difficulty maintaining sleep, waking up too early, or sleep that is chronically non-restorative or poor in quality" (Berger, 2009, p. 166). In general, any real or perceived disruption in sleep pattern that results in altered daytime function, as defined by the patient, is considered a sleep disturbance (Berger). While there can be physiological and psychological sources of sleep pattern disruption, oncology patients are at an increased risk for physiologic disturbances, as the "cancer process may play a prominent role in disrupting sleep, circadian rhythms, and hypothalamic-pituitary-adrenal axis-regulated processes" (Berger, p. 165).