Day-to-day variation in saliva cortisol—Relation with sleep, stress and self-rated health

Cortisol levels varied significantly among participants, with low morning levels linked to greater sleepiness and anxiety.

• Cortisol values exhibited both inter-individual and intra-individual variation over the study period.
• Low morning cortisol levels were associated with increased sleepiness upon waking and higher levels of anxiety and exhaustion the previous day.
• High cortisol levels in the evening correlated with reported symptoms of stress and poor self-rated health.
• Participants demonstrated a mixture of positive and negative cortisol awakening responses, affecting their immediate post-awakening behavior.
• Negative cortisol responses in the morning were linked to prolonged time spent in bed after waking, suggesting potential snoozing behavior.

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