Abstract:

BACKGROUND: Bifidobacterium and Lactobacillus in the gut have been suggested to have a beneficial effect on stress response and depressive disorder. We examined whether these bacterial counts are reduced in patients with major depressive disorder (MDD) than in healthy controls.
METHOD: Bifidobacterium and Lactobacillus counts in fecal samples were estimated in 43 patients and 57 controls using bacterial rRNA-targeted reverse transcription-quantitative polymerase chain reaction
RESULTS: The patients had significantly lower Bifidobacterium counts (P=0.012) and tended to have lower Lactobacillus counts (P=0.067) than the controls. Individuals whose bacterial counts below the optimal cut-off point (9.53 and 6.49log10 cells/g for Bifidobacterium and Lactobacillus, respectively) were significantly more common in the patients than in the controls for both bacteria (Bifidobacterium: odds ratio 3.23, 95% confidence interval [CI] 1.38-7.54, P=0.010; Lactobacillus: 2.57, 95% CI 1.14-5.78, P=0.027). Using the same cut-off points, we observed an association between the bacterial counts and Irritable bowel syndrome. Frequency of fermented milk consumption was associated with higher Bifidobacterium counts in the patients.
LIMITATIONS: The findings should be interpreted with caution since effects of gender and diet were not fully taken into account in the analysis.
CONCLUSION: Our results provide direct evidence, for the first time, that individuals with lower Bifidobacterium and/or Lactobacillus counts are more common in patients with MDD compared to controls. Our findings provide new insight into the pathophysiology of MDD and will enhance future research on the use of pro- and prebiotics in the treatment of MDD.

日本語要旨:

43人の大うつ病性障害患者と57名の健常者の腸内細菌について、善玉菌であるビフィズス菌と乳酸桿菌の菌数を比較したところ、うつ病患者群は健常者群と比較して、ビフィズス菌の菌数が有意に低いこと、さらにビフィズス菌・乳酸桿菌ともに一定の菌数以下である人が有意に多かった。この結果から、善玉菌が少ないとうつ病リスクが高まることが示唆された。