Rosalba C. wrote
http://www.wellbeing.com.au/natural_health_articles?cid=7157&pid=17353
The effects of altitude on the functioning of the brain and neuroendocrine system are very interesting. The Eastern tradition of spiritual aspirants going to the mountains to purify the mind and elevate the spirit might have a physiological basis. The neurotransmitters dopamine and seratonin, associated with positive mood and calmness, showed quite a significant increase in people who underwent a three-week course of intermittent hypoxic acclimatisation. Norepinephrine, the neurotransmitter associated with increased activity of the sympathetic nervous system and the so-called ‘fight or flight’ response, was decreased.