The Spielman 3P and Cano-Saper models of insomnia focus on the role of stress in the development of insomnia. To date, the impact of both naturalistic stressors and experimental stressors upon sleep have been inconsistent, due to limitations including the varied nature of the stressor, the diverse nature of participants and the lack of standardised experimental protocols for measuring stress and sleep. In addition, previous research has tended not to include an objective marker of stress, and thus cannot confirm that the stressor employed reliably elicits physiological stress. This thesis aimed to examine the effects of stress upon sleep, firstly developing and testing a standard protocol to measure both subjective and objective stress and sleep in the same context. Cortisol, specifically the cortisol awakening response (CAR), was measured as a physiological marker of hypothalamic-pituitary-adrenal (HPA) axis activity and objective sleep was measured using polysomnography. The protocol was used in an experiment to examine the impact of anticipation on sleep and stress, and then tease apart the impact of anticipation and anticipation coupled with demand, on sleep and the CAR. The results of the thesis indicate that anticipation of stress alone is sufficient to disrupt subjective sleep, when teased apart from demand. The results of the thesis also indicate that the CAR is a marker of anticipation and with a potential secondary role as a marker of recovery. Theoretically, the thesis indicates that the precipitating dimension within the Spielman 3P model occurs irrespective of whether the stressor is anticipated or actual.