Microbiome linked to depression in major studies

Dutch researchers say they have delivered the most extensive evidence to date of a relationship between the composition of the microbiome — ie, the variety of microorganisms that live on and in the human body — and instances of depression. Their research has been published in two papers in the journal Nature Communications

The research involved 3211 participants from the HELIUS study, which was initiated by Amsterdam UMC and GGD Amsterdam in 2010 in order to gain insight into health differences among Amsterdammers with a multi-ethnic background in an urban environment. It showed that a microbiome containing less diverse bacteria, or in which certain bacterial species are underrepresented, was associated with having depression or more depressive symptoms. This association was as strong as established risk factors for depression such as smoking, alcohol consumption, a lack of exercise and being overweight.

Influencing the microbiome may therefore be hugely relevant for the treatment of depression. Anja Lok, a psychiatrist and researcher at Amsterdam UMC, said, “Now that we know which disturbances in the microbiome are significant for depression, this opens up new possibilities for treatment and prevention, which is urgently needed.”

Microbiome composition also appears to play a role in the differing rates of depression across different ethnic groups. Previous research from the HELIUS study had illustrated ethnic differences in both the composition of the microbiome and the occurrence of depression, but until now there was no known connection between the two.

“The substantial ethnic differences in depression do indeed appear to be related to ethnic differences in the microbiome. We don’t know exactly why this is yet,” said researcher Jos Bosch, from the University of Amsterdam. “This association was not caused by differences in lifestyle such as smoking, drinking, weight or exercise, and merits further investigation. For example, diet could play a role.”

In the second paper, data from the HELIUS study was compared with the ERGO study, a long-term population study by Erasmus MC among people aged 40 and older in Rotterdam. This comparison confirmed a consistent association between 12 groups of bacteria and the occurrence of depression. It also offered an explanation: the 12 bacterial groups produce substances such as glutamate, butyrate, serotonin and gamma amino butyric acid — neurotransmitters that play an important role in depression.

“These results therefore clearly provide direction for future research into possible treatments, such as the use of probiotics, prebiotics and synbiotics or faecal microbiota transplantation as well as changes to lifestyle and diet,” Lok said.