Evaluating the Efficacy of Probiotics as an Adjunct to Behavioral Therapy in Patients With Overactive Bladder (OAB) and Anxiety Symptoms: A Randomized, Double-Blind, Placebo-Controlled Trial

Background and Scientific Rationale Overactive bladder (OAB) is a prevalent chronic condition that severely impairs patients' quality of life. Accumulating epidemiological evidence highlights a high comorbidity rate between OAB and psychological disorders, particularly anxiety. These two conditions often exacerbate each other, forming a vicious pathological cycle: anxiety heightens central sensitivity to bladder fullness, while unpredictable urinary urgency worsens psychosocial stress. Current pharmacological mainstays, such as antimuscarinics and β3-adrenoceptor agonists, primarily target local bladder smooth muscle. They often fail to address the underlying psychological comorbidities and are frequently associated with intolerable adverse effects (e.g., dry mouth, constipation), leading to high discontinuation rates. There is an urgent clinical need for systemic, well-tolerated therapeutic strategies that address both physical and emotional symptoms.

Theoretical Framework: The Brain-Gut-Bladder Axis This trial is grounded in the emerging "Brain-Gut-Bladder Axis" model. Chronic stress and anxiety can trigger systemic low-grade inflammation and alter the gut microbiome, which in turn influences peripheral neural pathways and bladder afferent signaling. We hypothesize that targeted microecological interventions using specific "psychobiotics" can modulate this axis. Scientific literature suggests that select probiotic strains can communicate with the central nervous system via the vagus nerve and systemic metabolites. By doing so, they may downregulate the hypothalamic-pituitary-adrenal (HPA) axis, optimize the levels of inhibitory neurotransmitters (such as GABA and Serotonin), and suppress neurogenic inflammation.

Intervention Strategy To test this hypothesis, this study employs an "add-on" clinical trial design. All enrolled participants will receive standardized behavioral therapy, which remains the fundamental first-line treatment for OAB, consisting of bladder training and lifestyle modification instructions. On top of this standard of care, participants will be randomized to receive either a multi-strain probiotic compound or a visually and organoleptically matched placebo.

The active intervention utilizes a compound of food-grade, widely recognized safe bacterial strains: Lactobacillus plantarum, Bacillus coagulans, Lactobacillus casei, and Lactobacillus acidophilus. These specific strains were selected for their documented potential in immune regulation, anti-inflammatory properties, and central nervous system modulation.

Study Execution and Clinical Significance Throughout the 12-week intervention period, the study avoids invasive procedures or the collection of extensive biological samples for complex genomic sequencing. Instead, it relies on validated clinical instruments, patient diaries, and standard routine urinalysis (strictly for safety monitoring and infection exclusion) to track treatment trajectories.