Thermal therapies–using heat and cold to stimulate the body–have become increasingly more common in American culture. You may have heard of the terms “cold plunge,” “cryotherapy,” “sauna bathing,” “whole body heating,” or even “hot/cold cycling,” also known as contrast treatment. Often, these modalities are used among athletes after intense physical exertion, to promote recovery. However, the scientific community is beginning to recognize the powerful effects of cold plunges on mental health and wellbeing.
It turns out that heat and cold therapies have been used for thousands of years around the world to promote vitality. Ancient Swedish culture is credited with hot-cold temperature cycling, moving between a sauna and cold plunge. However, ancient Greeks are also well known for their use of cold baths to renew energy stores, and it is a frequent practice in Traditional Chinese Medicine to utilize hot and cold modalities for balancing internal energies. The long history of these therapies speaks to their intuitive healing powers, while the science provides explanation about what is going on.
Holistic Perspectives
Let’s have a look at this through an integrative perspective. Physiological data shows us that changes in immune function, hormone release, microbiome diversity, and nervous system activation are associated with varying states of mood and psychiatric symptoms. For example, chronic stress, while mentally distressing, commonly manifests as physical illness. Likewise, how the body feels plays a big role in day to day wellbeing.
A top-down approach to mental health treatment might be to use cognitive behavioral therapy to alter behaviors and biological functions, whereas a bottom-up approach intervenes at the body to activate the mind. Thermal therapy is one of these bottom-up approaches that, by altering a person’s sensory and perceptual experience, influences brain function and mood.
The autonomic nervous system (ANS) to a large extent mediates bottom-up thermal therapy. It’s divided into two parts: the sympathetic nervous system (our “fight or flight” response) and the parasympathetic nervous system (our “rest and digest” system). Having the flexibility to oscillate the tone of each of these two systems fluidly is important for holistic health. Thermal therapy, with its alternating hot and cold stimuli, offers a novel way to engage the ANS, in effect expanding and potentially retraining its ability to move easily between states of excitement and relaxation. Increased tolerance to temperature changes translates to a greater capacity for physiological recovery, mental resilience, and sense of wellbeing.
Research on Benefits of Heat Therapy
Research indicates that regular sauna use might help alleviate depressive symptoms. Elevating body temperature through heat exposure could reduce symptoms of major depressive disorder, with effects lasting six weeks post-treatment. More recent studies are uncovering the mysterious link between thermal regulation, especially heat, and mental health.
Heat stress appears to modulate the hypothalamic-pituitary-adrenal (HPA) axis, lowering levels of the stress hormone, cortisol. Saunas have been shown to activate the release of serotonin, a neurotransmitter associated with feelings of contentment. Heat induces a sweating response and increases blood flow, which helps in flushing out toxins, delivering oxygen to tissues, and improving both immune and cardiovascular health. Increased blood flow to the lungs and brain can then support respiratory health and cognitive function. It may be that heat therapy works by changing immune system function, an important mediator of the brain-body connection. Heat also relaxes muscles and soothes joint pain. Generally, saunas tend to improve mood, promote relaxation, and aid in emotional regulation.
Cold Therapy
A bout of cold therapy can reduce pain and inflammation; by instantly constricting blood vessels, cold exposure reduces swelling, muscle soreness, and joint pain—key contributors to chronic physical pain that often coexists with mental health conditions. The body then works to compensate for these changes, and longer-term effects include enhanced blood flow, similar to the effects of heat therapy. A surge of norepipenephrine and endorphins improves mood and attention; meanwhile, it has been shown that cortisol decreases. Because thermal changes are natural physiological stressors, regular heat and cold exposure trains the brain and body to better cope with fluctuating stress.
Conclusion
Cold plunges and saunas, alone and in combination, offer powerful benefits for the brain-body connection. Shifting into states of cold or hot engages the ANS in a way that promotes biological flexibility, recovery, and resilience. Increased tolerance for the range of physiological activity is critical for physical and mental health. Thus, hot and cold therapy is associated with a decrease in depression and anxiety symptoms. Whether through structured cold plunges, regular sauna sessions, or alternating between the two, these ancient practices offer modern benefits that support the interconnectedness of the brain and body.
