Sauna use is often promoted as a wellness practice to reduce stress and improve relaxation. The question of whether this heat therapy genuinely influences the body’s primary stress hormone, cortisol, is of growing interest. Cortisol is a naturally occurring hormone that plays a role in nearly every bodily system. Understanding how sauna exposure interacts with this hormone provides insight into the stress-relieving potential of a regular heat routine.
Understanding Cortisol
Cortisol is a steroid hormone produced by the adrenal glands, often called the body’s main stress hormone. It helps manage the “fight-or-flight” response by regulating metabolism, increasing blood sugar, and temporarily suppressing the immune system.
The hormone naturally follows a distinct 24-hour cycle, known as the diurnal rhythm. Cortisol levels are highest in the morning to promote alertness, and gradually decline throughout the day, reaching their lowest point around bedtime. Chronic stress can dysregulate this rhythm, leading to persistently elevated or mistimed cortisol.
Chronic elevation of cortisol is detrimental to long-term health, contributing to issues such as fatigue, weight gain, mood instability, metabolic dysfunction, and systemic inflammation. Activities that help restore a healthy cortisol rhythm are valuable tools for overall well-being.
Acute Physiological Response to Sauna Use
Stepping into a sauna immediately subjects the body to intense thermal stress, triggering a rapid physiological response. The body’s core temperature begins to rise, necessitating a response to prevent overheating. This initial reaction is driven by the sympathetic nervous system, the system responsible for the “fight-or-flight” response.
To dissipate heat, blood vessels near the skin rapidly widen, increasing blood flow to the skin’s surface. This circulatory adjustment causes the heart rate to increase significantly, mimicking the cardiovascular demands of moderate exercise. For healthy individuals, this acute, controlled challenge is a form of hormetic stress that can strengthen resilience over time.
During the session, the body is in a state of heightened sympathetic activity. However, the subsequent cool-down period prompts a favorable shift. As the body cools, the parasympathetic nervous system—the “rest and digest” system—becomes dominant. This transition from sympathetic challenge to parasympathetic recovery is a key mechanism behind the relaxation associated with sauna use.
The Research Connection Sauna Use and Cortisol Levels
The effect of sauna use on cortisol is highly dependent on the duration and intensity of the session. Acute, prolonged, or very intense heat exposure is perceived as a physical stressor, which can temporarily increase cortisol levels. Studies using traditional saunas at very high temperatures, such as 200°F (93°C) or higher, may show a transient spike in cortisol as the body tries to cope with the thermal load.
Conversely, short and moderate sessions are associated with decreased perceived stress and favorable modulation of the stress response. Research indicates that a single session can measurably reduce cortisol in the blood, especially when followed by a proper cool-down.
The long-term benefit comes from repeated, controlled exposure, which appears to blunt cortisol reactivity. This means the body becomes more resilient and handles stress more gracefully over time. Regular sauna bathing regulates the stress response, which may lead to lower baseline chronic cortisol levels. The therapeutic benefit promotes better regulation of the entire stress axis for improved long-term stress management.
Practical Guidance for Stress Reduction
To maximize relaxation and avoid triggering an excessive stress response, duration and temperature must be carefully managed. For a traditional Finnish sauna, a temperature range of 150°F to 175°F (65°C to 79°C) is recommended for stress relief. Sessions should be limited to 10 to 20 minutes, which is sufficient to achieve beneficial physiological effects without undue physical strain.
For infrared saunas, which operate at lower temperatures, the ideal range is 120°F to 140°F (49°C to 60°C), allowing for sessions of 15 to 30 minutes. Consistency is more impactful than intensity; aiming for three to four sessions per week promotes superior results for long-term stress regulation. Proper hydration is mandatory before and after the session.
A gradual cool-down period after leaving the heat is important to facilitate the shift to the parasympathetic state. Individuals with pre-existing cardiovascular conditions or those who are pregnant should consult a healthcare professional before beginning a sauna routine. If any session causes dizziness or discomfort, exit immediately.