Effects of balneotherapy and spa therapy on levels of cortisol as a stress biomarker: a systematic review.

Antonelli M1, Donelli D
Int J Biometeorol. 2018 Jun;62(6):913-924. doi: 10.1007/s00484-018-1504-8. Epub 2018 Feb 18

https://www.ncbi.nlm.nih.gov/pubmed/29455296