Researchers in Prague put young men through three separate hour-long water immersions, at a comfortable 32 degrees Celsius, a cooler 20 degrees, and a cold 14 degrees, then measured hormones in their blood afterward.
At 14 degrees, plasma dopamine rose by about 250 percent and noradrenaline by about 530 percent, far beyond what the milder temperatures produced, while metabolic rate climbed roughly 350 percent as the body worked to stay warm.
The rise was driven by the sympathetic nervous system kicking into high gear against the cold, not by any drug or deliberate mental effort, and dopamine in blood is not the same as dopamine in the brain. The finding has since fed into popular interest in cold plunges for mood and focus, though this particular study measured hormones in blood, not mood or behavior directly.
Read the original study
Šrámek et al., European Journal of Applied Physiology, 2000 · doi.org/10.1007/s004210050065
Cold water, and a flood of dopamine.
Source
- Srámek, P., Simecková, M., Janský, L., Savlíková, J., & Vybíral, S. (2000). Human physiological responses to immersion into water of different temperatures. European Journal of Applied Physiology, 81(5), 436–42. https://doi.org/10.1007/s004210050065