The maritime profession is an extreme test of the crew’s mental health. Psychobiotics are live bacteria that improve the gut microbiome and benefit the host’s mental health. The study aims to establish the effect of a probiotic containing Lactobacillus bulgaricus DWT1 on the mental resilience of the crew of the St. St. Cyril and Methodius research ship during the First Bulgarian Military Antarctic Expedition during the 127-day journey to Antarctica. The crew was divided into two groups: the first took the probiotic, and the second did not. Zung questionnaires were used to test anxiety and depression levels in everyone before departure and after return. We used the Wilcoxon test to analyze data from sleep quality assessments. The individuals taking the probiotic showed no statistically significant differences in anxiety and depression levels before and after the journey and maintained sleep quality under the expedition’s extreme conditions. The ones not taking the probiotic had a significant increase in anxiety and depression levels, which correlatively worsened physiological sleep. The journey of the military ship crew to Antarctica is a model for studying the effects of probiotics containing Lactobacillus bulgaricus DWT1 on the mental health of people subjected to extreme stress. The probiotic’s formula is psychobiotic, maintains the gut-brain axis, protects against depression and anxiety and improves physiological sleep under stress.

Antarctica, depression, Lactobacillus bulgaricus, Naval Academy, probiotic