Background
Major depressive disorder impacts approximately 264 million people worldwide and is a leading cause of the global disability burden. In major depressive disorder (MDD), cognitive dysfunctions strongly contribute to functional impairments but are hardly addressed in current therapies. Novel treatment strategies addressing cognitive symptoms of depression are needed. As the gut microbiota-brain axis is linked to depression and cognition so the effect of a 4-week high-dose probiotic supplementation on cognitive symptoms in depression needs to be investigated. Probiotics may also improve several cognitive functions like verbal episodic memory, in healthy individuals, patients with major depressive disorder, Alzheimer’s disease, and other disorders.
Methods
- 60 patients with major depressive disorder were included in this randomized controlled trial, of which 43 entered modified intention-to-treat analysis.
- A probiotic supplement or an indistinguishable placebo containing maltose was administered over 31 days in addition to treatment as usual for depression.
- Participant scores on the Verbal Learning Memory Test (VLMT), Corsi Block Tapping Test, and both Trail Making Test versions as well as brain-derived neurotrophic factor levels were evaluated at three different time points: before, immediately after, and 4 weeks after intervention.
- Also, brain activation changes during working memory processing were examined before and immediately after the intervention.
Results
- A significantly improved immediate recall in the Verbal Learning Memory Test in the probiotic group immediately after intervention was found.
- Also, a time × group interaction in the hippocampus activation during working memory processing was found revealing a remediated hippocampus function in the probiotic group.
Conclusion
Additional probiotic supplementation enhances verbal episodic memory and affects neural mechanisms underlying impaired cognition in major depressive disorders. The present findings support the significance of the gut microbiota-brain axis in major depressive disorder and emphasize the potential of microbiota-related regimens to treat cognitive symptoms in depression.