More than half of the studies in a new systematic review found that regulating intestinal microbiota by adjusting diet or taking probiotic supplements reduced symptoms of anxiety, according to results published in the journal General Psychiatry.
“In the clinical treatment of anxiety symptoms, in addition to the use of psychiatric drugs for treatment, we can also consider regulating intestinal flora to alleviate anxiety symptoms,” researchers wrote. “Especially for patients with somatic diseases who are not suitable for the application of psychiatric drugs for anxiety treatment, probiotic methods and/or nonprobiotic ways … can be applied flexibly according to clinical conditions.”
The systematic review included 21 studies that involved 1503 participants. Fourteen of the studies used probiotics (7 used 1 probiotic, 2 used 2 kinds of probiotics, and 5 used supplements containing at least 3 types of probiotics) and 7 used nonprobiotic interventions, such as dietary change, to regulate intestinal microbiota.
In all, 11 of the 21 studies, or 52%, found regulating intestinal microbiota had a positive effect on anxiety symptoms, according to the review.
Six of the 7 studies that used nonprobiotic interventions, or 86%, found the approach to be effective for reducing anxiety, compared with 36% of studies that used probiotics as an intervention, researchers reported. In the 5 studies that used treatment as usual in addition to interventions to regulate intestinal flora, only nonprobiotic interventions were associated with a decrease in anxiety symptoms.
The fact that nonprobiotic interventions outperformed probiotic interventions may suggest that alteration of diet, a diverse energy source, may do more to influence gut bacteria than introducing specific bacteria types through a probiotic supplement, researchers reasoned. In studies that used several types of probiotics, the various types may have fought one another, they added, or intervention times in the studies may have been too short to significantly increase the abundance of probiotic bacteria imported.
Because of differences in research design types, subjects, interventions, and anxiety assessment scales, however, the data in the review was not suitable for meta-analysis, researchers explained.
“Therefore,” they concluded, “more relevant clinical intervention studies should be carried out with unified anxiety assessment scales and statistical methods being used to clarify the relationship between intestinal flora adjustment and improvement of anxiety symptoms.”