Isolated psychosis during exposure to very high and extreme altitude - characterisation of a new medical entity

Abstract

Background: Psychotic episodes during exposure to very high or extreme altitude have been frequently reported in mountain literature, but not systematically analysed and acknowledged as a distinct clinical entity.

Methods: Episodes reported above 3500 m altitude with possible psychosis were collected from the lay literature and provide the basis for this observational study. Dimensional criteria of the Diagnostic and Statistical Manual of Mental Disorders were used for psychosis, and the Lake Louise Scoring criteria for acute mountain sickness and high-altitude cerebral oedema (HACE). Eighty-three of the episodes collected underwent a cluster analysis to identify similar groups. Ratings were done by two independent, trained researchers (κ values 0.6-1).FindingsCluster 1 included 51% (42/83) episodes without psychosis; cluster 2 22% (18/83) cases with psychosis, plus symptoms of HACE or mental status change from other origins; and cluster 3 28% (23/83) episodes with isolated psychosis. Possible risk factors of psychosis and associated somatic symptoms were analysed between the three clusters and revealed differences regarding the factors 'starvation' (χ2 test, p = 0.002), 'frostbite' (p = 0.024) and 'supplemental oxygen' (p = 0.046). Episodes with psychosis were reversible but associated with near accidents and accidents (p = 0.007, odds ratio 4.44).

Conclusions: Episodes of psychosis during exposure to high altitude are frequently reported, but have not been specifically examined or assigned to medical diagnoses. In addition to the risk of suffering from somatic mountain illnesses, climbers and workers at high altitude should be aware of the potential occurrence of psychotic episodes, the associated risks and respective coping strategies.

Keywords: Acute mountain sickness; altitude; high altitude cerebral oedema; psychosis; schizophrenia.

Fig. 1.

Diagram displaying the relationship of psychosis, mental status change and HACE. Overall 102 episodes were analysed (absolute numbers in brackets) of which 83 episodes were included in the final analysis. + With mental status change; * without mental status change; § psychosis from other origin includes cases with mental status change due to, e.g. infection, dehydration or drugs. HACE: high-altitude cerebral oedema.

Fig. 2.

Bar chart depicting the duration of the episodes in the three clusters. The duration differed between the three clusters (χ² test, p = 0.031), with episodes in the PSY^PLUS cluster lasting longer than those in the PSY^NO and PSY^ISO clusters (z-test < 0.05 for PSY^{NO a}, PSY^{PLUS b}, PSY^{ISO a}). For z-test, each superscript letter denotes a subset of categories whose column proportions do not differ significantly from each other at the 0.05 level.