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< Supporting Evidence

Hallucinatory Experiences at High Altitude

(Letter to the Editor)

Eduardo Garrido, Casimiro Javierre, Josep L. Ventura, and Ramon Segura
Neuropsychiatry, Neuropsychology, & Behavioral Neurology, April 2000, 13 (2): 148-148.


Brugger et al recently reported a high incidence of hallucinatory experiences in seven of a group of eight European elite climbers during ascents at extgreme altitude in the Himalayas.

We studied 33 Spanish climbers with mean age 32.5 (5.3 SD) who had ascended to over 7,500 m on at least one occasion. Eleven (32.3%) had experimented hallucinatory episodes at high altitude and, by means of an accurate and structured interview, we detected a total of 16 instances: six somesthetic illusions (especially the sensation of imaginary accompanying presence behind one's own body), six auditory hallucinations (human voices, strange sounds of a musical nature), and four visual hallucinations (movement of objects, visualization of animals). None of the subjects experienced tactile, olfactory, or gustatory hallucinations. All these episodes happened at extreme altitude (>6,000 m), with two exceptions occurring at 49 m and 5,600 m above sea level. Their duration ranged between brief seconds and 3 hours, approximatley.

Our data is strongly in accordance with the reported study, basically in terms of type and duration of hallucinatory experiences, with somesthetic modality as the most frequent presentation during solo climbing above 6,000 m. Likewise, these experiences were not related with neuropsychological impairment or magnetic resonance imaging brain abnormalities found after extreme altitude exposure in the previous respective investigations. However, the greater overall incidence of hallucinatory instances and their percentage of affected subjects may be justified by the higher altitude reached and accumulated climb-time at extreme altitudes in the case of world-class professional mountaineers selected by Brugger et al. ...