Key Points:
Cortisol is the main output of the body’s hormonal response system.
Cortisol follows a known time course, peaking in the morning and dropping throughout the day among healthy individuals.
Cortisol can be measured in blood, hair, and saliva.
Cortisol is dynamic. It helps the body respond to stress by activating the body and also helps the body quiet down and regulate after the stressor is passed.
Cortisol has become a common biomarker of stress responding and is linked with variability across psychological and physical health.
Cortisol is the primary naturally-occurring steroid hormone made in the adrenal glands, small triangular-shaped glands that help regulate the body during stress. Once released into the bloodstream it travels throughout the body to help with a wide array of vital processes. These processes, like the regulation of blood pressure and immune function, all work together to help provide the body with energy. Blood levels of cortisol vary from person to person, but for most people cortisol is highest immediately upon first waking up to help prepare for the tasks ahead and then falls throughout the day hitting the lowest point in the evening, a pattern called diurnal rhythm. Additionally, when stressors occur heightened levels of cortisol can be released to help the body adaptively respond which is why some call it the “stress hormone.” The release of cortisol into the bloodstream can help provide the body with increased energy to face stressors, and has become a reliable metric of biological response to stress. One of the main targets of cortisol activation is the autonomic nervous system, which unconsciously regulates bodily functions (e.g., breathing). Importantly, cortisol not only revs the body up to respond to stress, but also helps calm the body down after the stressor has passed. When cortisol levels in the blood become high it then induces a negative feedback mechanism, telling the brain to terminate the stress response. Thus, while a metric of activation of stress response, high cortisol after stress is considered adaptive in that it serves an important role in shutting down further secretion of stress hormones.Cortisol levels peak in blood 10-30 minutes following stress exposure and can be measured via blood draws, levels are also well-detected in saliva 20 minutes after stress exposure and can be collected by swabbing a cotton ball along the inner cheek, less commonly cortisol can also be measured from hair samples. While all human body’s release cortisol, individuals vary with some producing too little and others producing too much, either extreme can be associated with negative health outcomes. Cortisol responding can be modified by various factors such as chronic stress, physical illness, and psychiatric conditions.It can also be intentionally modified by exercise and breathing exercises.
