Metabolic complications blunt benefits of probiotics on depression, data suggests

The trial missed its primary goal as a probiotic proved no more effective than placebo at relieving depression symptoms over 60 days of treatment.

However, a subgroup of participants that responded very well to the treatment tended to have a lower body mass index (BMI) than others in the same group, with average scores of 23.17 and 25.07 respectively. They also had lower hepatic steatosis index and a lower quality of life score, observed the researchers.

Glenn Gibson (University of Reading, Reading, UK), who wasn’t involved in the research, said that the study was “very well conducted and described” relating to which types of probiotics might help in treating depression. Using another species of bacteria and the use of prebiotics could have given more enhanced effects, he added.

Depression, which involves lowered mood levels and a loss of energy, affected 280 million people around the world in 2019, including 5% of all adults​. This condition alone costs the global economy around $1 trillion in lost productive days and is linked to metabolic syndrome disorders including obesity, hypertension and insulin resistance.

The gut microbiome plays a role in modulating mental health via the microbiota-gut-brain axis, and probiotic treatments have often been studied as potential strategies for tackling depression. In general, however, the treatments have only been effective as an add-on therapy, say Gawlik-Kotelnicka and colleagues.

In the double-blind controlled trial, the researchers enrolled people over 18 years old in Poland with a diagnosis of depression based on the 11th International Classification of Diseases (ICD-11), and with a score of 13 or more on the clinician assessed Montgomery–Asberg Depression Rating Scale (MADRS) score, which ranges from 0 to 60 where a higher score indicates more severe symptoms.