Many mountaineers and high altitude climbers have experienced this: while exposed to very high or extreme altitude they suddenly sense the presence of another person, sometimes just a shadow, sometimes they could see the person clearly and engage her or him in conversation. The person would comment on their climbing progress or give advice on how to proceed. Other climbers have seen trees and mountain huts, smelled cooked food or where convinced that they could fly.

When we (Hermann Brugger and Katharina Hüfner) were ski touring together at high altitude in Tajikistan, one night, while sitting next to a wood-fire stove and drinking beer (not recommended at high altitude) we discussed that looking at these experiences in a systematic and scientific way would be an interesting project. Luckily, we had the scientific background to do so being an emergency physician specialized in altitude medicine and a neurologist now working in psychiatry, both with a love for mountains.

Together with a team of researchers we analyzed 102 episodes (83 of which were included in the final analysis) from the lay mountain literature. These included reports, among others, from Lincoln Hall, Hermann Buhl, Steve House and Reinhold Messner. We used a computer program designed for qualitative data analysis to label psychiatric and somatic symptoms, as well as tour related information, in the text passages. We then extracted a database which was used for a cluster analysis. This means that a computer algorithm searches for “cases” (here: climbing episodes) with similar characteristics. Three clusters were identified: The first cluster consisted of episodes where no symptoms of psychosis occurred, the second cluster contained episodes with symptoms of psychosis related to medical conditions such as high altitude cerebral edema (HACE), infection or other identifiable somatic causes. Subjects in these episodes showed signs of reduced consciousness or confusion. And finally, cluster three included episodes where psychotic symptoms occurred unrelated to a somatic condition. We termed the latter “isolated psychosis” cluster. Isolated psychosis is a previously not recognized medical entity.

Most importantly, we found that psychotic symptoms are related to an increase in near-accidents and accidents on the mountain. This is very relevant since knowing about the danger of psychotic symptoms could help prevent accidents not only while climbing, but also while working at high altitude or during aviation. We thus propose that individuals going to high altitude should be educated about psychotic symptoms just as they are informed about somatic altitude-related disorders. This could help them recognize the symptoms in themselves or in a partner. Cognitive strategies such as reality testing, which have been used to treat psychotic symptoms at sea level, should be practiced beforehand. As far as we can see from this study, the symptoms disappear completely as soon as the individual leaves the danger zone– furthermore, there does not appear to be any consequential damage. This discovery might allow us to study temporary psychoses in otherwise healthy people, an investigation which might yield important indications for the understanding of psychiatric diseases such as schizophrenia.

Next spring, we plan to collaborate with Nepalese doctors by undertaking further investigations in the Himalayas. We hope to find out, inter alia, how frequently this disease occurs and what the predisposing factors are, so that, in the future, we might be able to identify individuals at risk for developing psychotic symptoms at altitude.

Learn more about Katharina Hüfner and Hermann Brugger’s Open Access article, Isolated psychosis during exposure to very high and extreme altitude – characterisation of a new medical entity, published in Psychological Medicine.

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