Could probiotics play a real role in ameliorating major depressive disorder?

Probiotics may help decrease symptoms of depression when administered adjunctively to antidepressants and appear to have good safety. In a study published in JAMA Psychiatry, researchers in the U.K. describe the results of a pilot randomized clinical trial on the acceptability, tolerability and effectiveness of probiotics as an adjunctive treatment in major depressive disorder (MDD). The study built on previous work they published in 2021 in which a meta-analysis of seven randomized clinical trials (RCT), including 404 patients, suggested the treatment approach was effective. “However, several RCTs to date have not provided sufficient tolerability data, while others report poor adherence or retention,” they wrote. The trial included 49 participants, aged 18 to 55 years, with a primary diagnosis of MDD and with a Hamilton Depression Rating Scale (HAMD-17) score greater than 13. A total of 80% were female and the mean age was 31.7 years. All participants were taking an antidepressant for six weeks or more and had an incomplete response to the medication. Forty-five of the 49 participants were taking a selective serotonin reuptake inhibitor (SSRI), and 43% met criteria for generalized anxiety disorder. Twenty-four participants were in the probiotic group and 25 in the placebo group. Participants took either a multistrain probiotic (8 billion colony-forming units per day) or a placebo daily for eight weeks. Data were collected between September 2019 and May 2022. Depressive symptoms for both groups improved over eight weeks with a greater reduction of symptoms in the probiotic group at week four and eight according to HAMD-17 scores and Inventory of Depressive Symptomatology (IDS) scores. There was also a greater improvement in anxiety scores in the probiotic group at week four and eight, according to the Hamilton Anxiety Rating Scale (HAMA) scores, but not General Anxiety Disorder (GAD-7) scores, compared to the placebo group. The clinical trial had an attrition rate of 8% (one in the probiotic group and three in the placebo group) and adherence rate of 97.2 % of doses taken as required (capsule count). The authors reported that the intervention was well tolerated with no serious adverse reactions and no dropouts due to adverse effects. “The estimated effect sizes on key clinical outcomes are promising and encourage further investigation in a definitive efficacy trial,” wrote the authors of the study.

Could probiotics play a real role in ameliorating major depressive disorder?

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