Efficacy of a multispecies probiotic as adjunctive therapy in generalized anxiety disorder: a double blind, randomized, placebo-controlled trial

Objectives: Studies have shown that probiotics may decrease anxiety symptoms, but to our knowledge so far no trial has investigated the effects of probiotics in generalized anxiety disorder (GAD). The aim of the present study was to determine the effects of probiotics as adjunctive therapy on anxiety severity and quality of life (QOL) in patients with GAD. Methods: Forty-eight drug-free patients with a diagnosis of GAD based on DSM-V criteria were randomly assigned to two groups to receive daily either one capsule of probiotics or placebo in addition to 25 mg sertraline for 8 weeks. Probiotic capsules contained 18*10(9) CFU Bifidobacterium longom, Bifidobacterium bifidum, Bifidobacterium lactis and Lactobacillus acidophilus bacteria. Results: Intention to treat analysis was performed in 39 Patients who completed at least 4 weeks of the intervention. After 8 weeks, the score of Hamilton Rating Scale for anxiety (HAM-A) decreased more in the probiotics + sertraline (PS) group (p = 0.003). Although the reduction of Beck Anxiety Inventory (BAI) was also more in the PS group, it was not significantly different from that of the sertraline alone(S) group. Moreover, despite the greater reduction of State-Anxiety Inventory score in the PS group, the score of Trait-Anxiety Inventory was not statistically different between the two groups at week 8. With regard to QOL, there was no significant difference between the two groups in the change of the score of QOL domains. Conclusions: Probiotics + sertraline combination was superior to sertraline alone in decreasing anxiety symptoms after 8 weeks in patients with GAD, although it did not affect QOL.