Which hormone is associated with morning wakefulness and stress?

• A. Melatonin
• B. Dopamine
• C. Cortisol
• D. Serotonin

Answer: (C)

Cortisol is the hormone most closely tied to both morning wakefulness and the body's stress response. It’s produced by the adrenal cortex under the control of the hypothalamic–pituitary–adrenal (HPA) axis and follows a diurnal rhythm. Levels rise in the early morning, creating the cortisol awakening response that helps increase energy availability and alertness as you start the day. When stress is present, CRH from the hypothalamus triggers ACTH release from the pituitary, which stimulates cortisol release to mobilize energy and prepare the body for action.

Melatonin signals darkness and promotes sleep, so it is highest at night and decreases toward morning, making it less associated with waking. Dopamine supports arousal and motivation but isn’t the primary hormone linked to the characteristic morning wakefulness and stress response described here. Serotonin influences mood and sleep regulation as well, but its role isn’t the defining factor in the morning wakefulness and stress pattern in the way cortisol is.