Table 1.

Known effects of cold stress. "Immediate/transient" means effects of a single brief exposure to cold that last less than 1–2 hours. "Sustained/longer-term" means effects (of repeated daily or several times per week cold-water stress) that can last one day or longer.

Immediate/transient effects	Sustained/longer-term effects
Activation of: sympathetic nervous system [15,16] hypothalamic-pituitary-adrenal axis [17,18] hypothalamic-pituitary-thyroid axis [19,20] Increased resting metabolic rate [29]	An increase in plasma levels of: adrenocorticotropic hormone [35] corticosterone* [3] interleukin-2 (modest/undetectable) [3,84] interleukin-6 [12] tumor necrosis factor-α [12] haptoglobin [12] hemopexin [12]
An increase in plasma levels of: adrenocorticotropic hormone [30,31] norepinephrine [15,16] beta-endorphin [18,32] corticosterone* [7] cortisol (modest/undetectable) [33,34,82,83] thyroid stimulating hormone [20] triiodothyronine [19,20] thyroxine [20] interleukin-6 [6,13] Decreased plasma level of interleukin-2 [84,85]	Decreased plasma levels of: α1-antitrypsin [12] testosterone [6]

* It is expected to have a negligible immunosuppressive effect [86,87].