In a recent clinical study, we demonstrated in the general population that Lactobacillus helveticus R0052 and Bifidobacterium longum R0175 (PF) taken in combination for 30 days decreased the global scores of hospital anxiety and depression scale (HADs), and the global severity index of the Hopkins symptoms checklist (HSCL-90), due to the decrease of the sub-scores of somatization, depression and anger-hostility spheres. Therefore, oral intake of PF showed beneficial effects on anxiety and depression related behaviors in human volunteers. From there, it is interesting to focus on the role of this probiotic formulation in the subjects with the lowest urinary free cortisol levels at baseline.

This addendum presents a secondary analyse of the effects of PF in a sub-population of 25 subjects with urinary free cortisol (UFC) levels less than 50 ng/ml at baseline, on psychological distress based on the percentage of change of the perceived stress scale (PSs), the HADs and the HSCL-90 scores between baseline and follow-up. The data show that PF improves the same scores as in the general population (the HADs global score, the global severity index of the HSCL-90 and three of its sub-scores, i.e. somatization, depression and anger-hostility), as well as the PSs score and three other sub-scores of the HSCL-90, i.e. "obsessive compulsive", "anxiety", and "paranoid-ideation". Moreover, in the HSCL-90, the score of the Factor 1, related to anxiety and depression, is significantly improved over time in PF-treated subjects compared with controls.

Additional preclinical data showed that PF formulation does not induce side effects such as addiction or learning and memory impairments, and therefore displays a good safety profile.

Complementary hypothetical mechanisms of action are proposed to explain the functioning of the brain-gut axis, particularly the relationship between probiotics and stress-related psychopathologies, such as anxiety and depression.