Cold Water Exposure: Treating Noradrenergic Dysfunction

The benefits of a cold shower, while largely anecdotal, are recommended for everything from hangovers to excessive libidos. Despite its reputation as a quasi-folk remedy, recent research suggests exposure to cold water may help treat depression, anxiety and even attention-deficit disorders. The invigorating effects of cold water are apparent to all of us who have accidentally opened the cold tap in the shower or purposefully jumped into a swimming pool. The shock of cold water on our skin generates an active and near immediate response from our sympathetic nervous system, the activity of which is regulated in the brain through the release of signaling molecules called neurotransmitters. Norepinephrine is the primary neurotransmitter responsible for the sympathetic “fight or flight” responses we experience during times of stress, panic and anger. The activity of the sympathetic nervous system can also be elicited by environmental stressors, like exposure to cold temperatures. Norepinephrine is synthesized primarily in the locus coeruleus, a region of the brainstem in constant communication with most of the forebrain (Stanford, 1995).

Šrámek and colleagues (2000) have shown that when participants were immersed in cold water (14°C) , there was a five-fold increase in plasmanoradrenaline/norepinephrine levels, as compared to baseline. An increase in noradrenaline concentration of that magnitude suggests a response mediated by the sympathetic nervous system. It is reasonable to assume that an individual exposed to coldstressors should display physiological and behavioral manifestations of sympathetic nervous system activity. Assessing the degree to which these changes differ between individuals may allow the extent of noradrenergic function or dysfunction to be measured and compared.

In rats, chronic exposure to cold temperatures affects the rate at which cells in the locus coeruleus adapt to an intracellular injection of current (Jedema & Grace, 2003). This suggests that norepinephrine-producing cells in the locus coeruleus were more rapidly able to adapt to disruptions in depolarization after chronic exposure to cold-stressors.

Additionally, increased excitability of neurons within the locus coeruleus was observed after the rats were chronically exposed to cold. These changes imply that the treatment was effective in modifying the self-regulatory capabilities and sensitivity of norepinephrine producing cells in the brain. The significance of these findings are in their validation that exposure to cold stressors can affect cellular changes in locus coeruleus neurons, and likely by extension, the behavior of the organism itself (Jedema et al., 2001). It would be interesting to determine the effects of acute exposure to cold stressors and whether the same changes in neuronal excitability are maintained for an extended duration.

Shevchuk (2008) contends that the origin of noradrenergic dysfunction in humans is partly due to individual genetic susceptibility and partly due to an evolutionary mismatch between our modern and ancestral environment. He believes that cold shower treatment can be used as therapy for depression and other conditions that may be related to noradrenergic dysfunction. Shevchuk also argues that modern humans lack sufficient “thermal exercise” of the locus coeruleus, of which our ancestors would have been subject to over the course of millions of years of evolution. Cost-effective methods of indoor climate control have only been developed within the last century and any behavioral symptoms rooted in a lack of “thermal exercise” would be exacerbated by climate-controlled lifestyles. It would be interesting to see whether the diagnosis of anxiety disorder or other conditions predicted by noradrenergic dysfunction increased following the introduction of affordable air-conditioning and cooling systems during the mid 20th century. In an era where climate controlled vehicles and buildings predominate it is clear that we are living in conditions significantly different than those of our hominid ancestors. Whether this environmental and thermal incongruity is responsible for the prevalence of anxiety and depressive disorders in modern society has yet to be determined, but the findings presented here suggest that cold temperatures can potentially treat depression and anxiety in humans.