Effects of Lactic Acid Bacteria in Patients With Attention-Deficit/Hyperactivity Disorder：An Open Label Clinical Research

In recent years, increasing attention has been directed toward the impact of lifestyle and dietary factors on cognitive function, mood, and sleep. Probiotics are defined as live microorganisms that, when administered in adequate amounts, confer health benefits to the host by modulating gut microbiota composition, intestinal barrier function, inflammatory responses, and antioxidant activity. Through these mechanisms, probiotics may contribute to host health by delaying disease progression, regulating pathological processes, and preventing disease-related complications. A growing body of basic and clinical evidence has further demonstrated associations between the gut microbiota, probiotic interventions, and a range of neuropsychiatric and neurodegenerative conditions, including stress-related disorders, autism spectrum disorder (ASD), anxiety, depression, and Parkinson's disease (PD).

In addition to live probiotics, increasing interest has been directed toward postbiotics, which are defined as preparations of inanimate microorganisms and/or their components that confer health benefits to the host. Postbiotics contain a variety of bioactive constituents, including cell wall components (such as peptidoglycans and lipoteichoic acids), intracellular contents, and microbial metabolites produced during fermentation. These components are known to interact with host immune and metabolic pathways, contributing to immunomodulatory, anti-inflammatory, antioxidant, and gut barrier-enhancing effects. Importantly, postbiotics may exert biological activities similar to those of live probiotics while avoiding several limitations associated with viable microorganisms.

The strain investigated in the present study is heat-treated Lactiplantibacillus plantarum. Although heat treatment abolishes its capacity for replication, the resulting postbiotic retains multiple bioactive components, including intact cell wall structures and postbiotic metabolites. Heat treatment also enhances product stability and shelf life, reduces sensitivity to environmental conditions, and ensures consistent dosing, thereby improving suitability for clinical application. From a safety perspective, postbiotics eliminate the risk of microbial translocation, infection, or horizontal gene transfer, which may be of particular concern in vulnerable populations such as children, the elderly, or individuals with compromised immune function. Consequently, postbiotics are increasingly regarded as a safe and reliable alternative to live probiotics in clinical research and practice.

Heat-treated Lactiplantibacillus plantarum has been investigated in several clinical contexts, including ASD, attention-deficit/hyperactivity disorder (ADHD), and Parkinson's disease, demonstrating potential benefits in modulating neurological and behavioral outcomes. Collectively, these findings support the rationale for further investigation of postbiotic interventions as a stable, safe, and biologically active strategy for targeting gut-brain axis-related conditions