The behavioral and psychological symptoms of dementia (BPSD) is a syndrome that is highly prevalent in older adults. BPSD encompass multiple pathological systems and are age- and stage-related. The long-term mission of our research group is to elucidate the mechanisms underlying the microbial–gut–brain axis in BPSD. We are committed to pushing the BPSD frontiers in social science and medicine through strict adherence to scientific integrity and ethical responsibility.