Effects of Postbiotics on Mood Disorders in Korean Adults

Epidemiology Research Center Depression Scale (CES-D):

The Center for Epidemiologic Studies Depression Scale (CES-D) is a widely used 20-item self-reported instrument designed to measure depressive symptom severity in the general population. Each item is rated on a 4-point scale (0 to 3), assessing emotional, somatic, interpersonal, and positive affect domains over the past week. Total scores range from 0 to 60, with higher scores indicating more severe depressive symptoms.

Ecological Momentary Assessment (EMA) captures real-time mood states by sending brief questionnaires to participants multiple times per day via online links. Each assessment includes six questions related to current mood and mental state, scored on a continuous slider scale from 0 (not at all) to 100 (very much). Higher scores indicate greater severity of negative mood or emotional distress. The average daily score will be calculated and used to assess change from baseline.

The Depression Anxiety Stress Scale (DASS-21) is a validated self-report tool containing 21 items, divided equally into three subscales: depression, anxiety, and stress. Each item is rated on a 4-point scale (0 to 3), and subscale scores are summed. Each subscale score ranges from 0 to 21, with higher scores indicating more severe symptoms in the respective domain.

The Perceived Stress Scale (PSS) is a validated 10-item self-report questionnaire assessing the degree to which situations in one's life are appraised as stressful. Each item is rated on a scale from 0 (never) to 4 (very often), with total scores ranging from 0 to 40. Higher scores indicate greater perceived stress.

Fecal samples will be collected for gut microbiota profiling using 16S rRNA gene sequencing. Participants will be asked to provide approximately 0.5 grams of stool in one container, collected within 24 hours prior to the clinic visit. The sample should be stored in a household freezer until delivery, and will be stored at -80°C upon arrival for microbial DNA extraction and analysis.

For metabolite analysis using ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS), participants will be asked to provide approximately 0.5 grams of stool in each of two containers. These samples should be collected within 24 hours prior to the clinic visit, frozen at home, and delivered in a frozen state. Upon receipt, samples will be stored at -80°C for metabolomic profiling.

The VAS-IBS is a self-report instrument that assesses gastrointestinal symptoms such as abdominal pain, bloating, diarrhea, constipation, and flatulence. Each symptom is rated on a visual analog scale from 0 (very severe) to 100 (very mild). Lower scores indicate more severe symptoms.