Mood states at 1600 and 4300 meters terrestrial altitude.

Personal anecdotes suggest that ascent to high altitude can cause mood changes such as depression, apathy, and drowsiness. Observed behaviors at high altitude indicate that people can become more euphoric, irritable, or argumentative. Since there are few systematic and quantitative studies assessing the effects of altitude on mood, this study compared moods measured at two different altitudes and times of day (morning-evening) using a standardized scale. Self-rated moods were determined twice daily in 19 males and 16 females with the Clyde Mood Scale. Baseline values were determined at 200 m; moods were then assessed at 4300 m with one group and at 1600 m with a second group. Friendliness, clear thinking, dizziness, sleepiness, and unhappiness were affected at 4300 m but only sleepiness changed at 1600 m. At 4300 m, the altered moods differed from baseline on the day of arrival (1-4 hours), differed even more after one day (18-28 hours), and returned to baseline by day 2 (42-52 hours). Morning and evening values were similar at each altitude. Therefore, changes in mood states at altitude have a distinct and measurable time course.