Efficacy of a Culturally-adapted Mediterranean Diet Intervention on Depression in Relation to the Gut Microbiome

The PHQ-9 is a 9-item questionnaire used for screening, diagnosing, monitoring and measuring the severity of depression, which scores each of the nine DSM-IV criteria from "0" (not at all) to "3" (nearly every day).

The GAD-7, a 7-item self-report questionnaire, was used to measure generalized anxiety symptoms. Each item is rated on a 4-point Likert scale, with response categories ranging from 'not at all' (0) to 'nearly every day' (3). The total score is the sum of the 7 items, with a range of 0 to 21.

The ISI is a 7-item scale designed to evaluate perceived insomnia severity. Ratings on the 5-point Likert scale are obtained on the perceived severity of sleep-onset, sleep-maintenance, early morning awakening problems, satisfaction with current sleep pattern, interference with daily functioning, noticeable of impairment attributed to the sleep problem, and level of distress caused by the sleep problem.

The ModiMedDiet Score is a 12-item criterion-based diet quality index ranging from 0-120, with higher scores indicating greater adherence to the Mediterranean diet pattern promoted in the SMILES dietary intervention trial. It assesses intake of 12 food groups based on recommended intakes. Scores were calculated for both intervention and control groups to measure compliance and dietary changes over time. An adherence level of ≥55.62 was defined as highest, and ≤33.65 as lowest. Extras intake (sweets, processed foods, fast food, sugary drinks) was also reported separately due to their less healthy profiles. An adapted version will be designed based on the original ModiMedDiet to reflect the food groups delivered to the MediDiet group in the current study.

The 7dFR is a self-reported record of all foods and beverages consumed over a consecutive 7-day period. Participants record descriptions of food/drink items, amounts consumed, brands, preparation methods and portion sizes for every eating occasion over the 7 days. Intakes are then analyzed using nutrition software to derive daily nutrient intakes.

The IPAQ-C is a 5-item self-report tool that measures time spent sitting, walking, in moderate activity, and vigorous exercise in the last 7 days. Responses are converted to minutes and reported as a continuous metabolic equivalent task (MET) minutes per week variable, with the exception of sitting time reported in hours. MET is a quantitative indicator of energy expenditure, with walking assigned 3.3 METs, moderate activity 4 METs, and vigorous activity 8 METs. A total physical activity score is calculated as the sum of walking and moderate to vigorous exercise MET-minutes. Higher total scores represent greater physical activity levels.

HRQoL will be evaluated using the Short Form (Six-Dimension) Health Survey (SF-6D; Lam et al., 2008). The participants select the levels (up to 4 or 6 levels) that best describe their physical functioning, role limitation, social functioning, bodily pain, mental health, and vitality. A preference-based single index measure is calculated by adding the scores of the 6 dimensions using a scoring algorithm. The total SF-6D score ranges from 0.315 (the worst HRQoL) to 1 (full health).

SDS is a brief, 5-item self-report tool that assesses functional impairment in work/school, social life, and family life.

TAS is a 15-item self-report measure used to assess parents' and caregivers' acceptability and willingness to implement a proposed treatment for their child. Respondents rate their level of agreement with statements about the treatment on a 7-point Likert scale ranging from 1 (strongly disagree) to 7 (strongly agree). Example items address the treatment's effectiveness, appropriateness, risks, and consent requirements. Scores are summed with higher total scores indicating greater treatment acceptability. The TAS provides a standardized tool for clinicians to evaluate parents' perceptions of interventions as part of the treatment selection process.

The 6-item CEQ yielded ratings of treatment credibility, acceptability/satisfaction, and expectations for success.

Fresh stool samples will be collected by participants using the gut microbiome test kit developed by BioMed Technology, Hong Kong.

The self-developed survey will collect basic demographic information such as age, gender, level of education, occupation, relationship status, height, weight, waist circumference, and body mass index (BMI).