From Gut to Grey Matter: Exploring the Gut–Brain Axis in Older Adults – Implications for Mental Health in Primary Care

The gut–brain axis (GBA) is a two-way communication system between the gastrointestinal tract and the central nervous system. Dysbiosis (alterations in the composition of the gut microbiota) has been linked to mental health outcomes in older adults. Dysbiosis in older adults is linked with increased inflammation, neurotransmitter dysregulation, and reduced cognitive resilience. Common medications such as antibiotics, proton pump inhibitors, and psychotropics can exacerbate microbial imbalance. Emerging therapies like probiotics and Mediterranean-style diets show promise in improving mental health outcomes. The GBA offers a clinically relevant, modifiable target for improving mental well-being in older adults. GPs and psychiatrists are well placed to integrate gut health awareness into holistic mental health assessments and care plans. This narrative review explores how the gut microbiota changes with age and how these changes may be connected to mental health conditions such as depression, anxiety, and cognitive decline. The review also considers how commonly used medications can affect the gut microbiome. Finally, it examines potential interventions—including probiotics, dietary strategies, and faecal microbiota transplantation (FMT)—that may help support mental well-being in older adults.