Sleep, Hormones, and Circadian Rhythms throughout the Menstrual Cycle in Healthy Women and Women with Premenstrual Dysphoric Disorder

Figure 1

The interaction between circadian (C) and homeostatic (S) processes in an “opponent-process” results in an uninterrupted 8-hour nocturnal sleep episode and a wake period maintained throughout the 16-hour day. The homeostatic drive for sleep (illustrated as the “sleep load”) increases throughout the waking period and reaches a peak just before habitual bedtime. The circadian drive for alertness (illustrated as the “alerting signal”) reaches a peak at this time and is lowest near the end of the sleep episode. From [8].