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alterations that occur under conditions of hypoxia, there have been few investigations of the mood and behavioral changes associated with altitude. This chapter discusses both field and laboratory studies conducted to assess changes in these parameters.

MOOD STATES

Observed behaviors and personal anecdotes suggest that the initial mood experienced at altitude is euphoria, followed by depression. With time, individuals may also become quarrelsome, irritable, anxious, and apathetic (Van Liere and Stickney, 1963). Unfortunately, although disturbances in emotional control have been noticed at altitude for decades, there are few quantitative studies assessing mood changes at altitude.

Shukitt and Banderet (1988) conducted one of the first systematic studies of mood changes at altitude. Self-rated moods were evaluated in 35 subjects using the Clyde Mood Scale. The Clyde Mood Scale (Clyde, 1963) consists of 48 adjectives rated on a 4-point scale: ''not at all," "a little," "quite a bit," and "extremely." These adjectives cluster into six mood factors: friendly, aggressive, clear thinking, sleepy, unhappy, and dizzy. Baseline values were determined at 200 m (656 ft); moods were then assessed for 2 days at 1,600 m (5,250 ft) in one group, or for 4 days at 4,300 m (14,110 ft, at the top of Pikes Peak) with a second group.

At 4,300 m (14,110 ft), moods differed from baseline (200 m [656 ft]) on the day of arrival (day 0) and differed even more after 1 day (Figure 22-1). Subjects became less friendly, less clear thinking, and dizzier. They also became sleepier and happier, while aggressiveness stayed the same (Figure 22-2). Only sleepiness changed at 1,600 m (5,250 ft), with the subjects becoming sleepier at this altitude compared to sea level. However, by day 2 after ascent to 4,300 m (14,110 ft), all changes had returned to baseline levels. Therefore, at 4,300 m (14,110 ft), the altered moods differed from baseline on the day of arrival (1 to 4 hours), differed even more after 1 day (18 to 28 hours), and returned to baseline by day 2 (42 to 52 hours). Mood states are thus adversely affected by both duration and level of altitude, and changes in mood states at altitude have a distinct and measurable time course.

In another study, Shukitt-Hale et al. (1990) evaluated mood states during a climb of Mount Sanford, Alaska to determine the extent to which mood was dependent not only on the altitude and rate of climb, but also on the length of stay and effort expended to reach the desired altitude. Self-rated moods were determined with the Profile of Mood States (POMS). This questionnaire (McNair et al., 1971) is a 65-adjective questionnaire, with the adjectives rated on a 5-point scale. It measures six mood factors: tension, depression, anger, vigor, fatigue, and confusion. Seven male volunteers from the U.S. Army were



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