The emerging concept of bidirectional signalling between the gut microbiota and the brain is an active field of research. Studies indicated that the gut microbiota can modulate the gut–brain axis via multiple mechanisms, including alterations in microbial composition or production of microbial neuroactive metabolites. Thus far, links have mostly been reported in animal models, and human studies are limited. Raes and colleagues now report a large population cohort study in which they correlate microbial taxa with quality of life and the incidence of depression. Butyrate-producing Faecalibacterium and Coprococcus spp. were associated with higher quality of life indicators. Moreover, Coprococcus spp. and Dialister spp. were shown to be depleted in participants with depression. Finally, the potential of microbial synthesis of a dopamine metabolite positively correlated with mental quality of life, possibly linking the neuroactive metabolic capacity of the gut microbiome with mental health.