4. Discussion
abdominal obesity, MetS, overweight, depressive disorders
SECONDARY, RECRUITMENT, COVID-19 INFECTION
This study was aimed to assess the feasibility of a larger RCT. The rate of enrolment was shown to be 6.5 participants per month, which was lower than expected. Several obstacles in the process were identified; however, most of them were not modifiable. One problem was posed by the lockdown procedures associated with the COVID-19 pandemic [More than half (52%) of the recruited participants were found to be eligible and then enrolled. This was in accordance with our hypothesis. The main problem regarding the final study population nesting was the insufficient proportion of participants with MetS. This may be partly due to recruiting younger participants not yet fulfilling the MetS criteria, despite being overweight or suffering from abdominal obesity. In addition, part of the recruitment process took place through notices on social media, and, due to the pandemic, the major part of the assessment process was undertaken on-line; this may have discouraged middle-aged or older people. Additionally, older subjects might have been more afraid of COVID-19 infection.It is not entirely surprising that a lower number of MetS patients was recruited than those without MetS, as only around one third of the population with depressive disorders suffer from comorbid MetS [The progression criteria, as previously outlined, was met, with the retention rate reaching the 80% threshold. This further confirms the feasibility of the full-scale RCT.Missing data and dropouts are issues in most RCTs, and were shown to be crucial for our study’s feasibility and data completeness procedures. Therefore, some changes were introduced even during the pilot study, and these are thoroughly described in the Results section.The pilot study hence raised several practical issues that can be addressed for the full RCT. In addition to those listed above, the study will incorporate a daily medication chart in paper form to improve the adherence to intervention. Moreover, various procedures, ranging from advertising the study to administering laboratory findings to study participants will be improved. For example, several ready-to-use text messages for different study stages have been designed in both paper and electronic form.The baseline participant age, sex, comorbidities, smoking status or anthropometric measures are similar to those reported in other studies investigating probiotics in populations with depressive disorders [A change in tertiary outcome measures were observed between time-points V1 and V2. All changes were given 95% confidence intervals. Interestingly, the mean MADRS score change was −5.47 points in PRO-D but only −2.54 in PLC-D; it has been suggested that an improvement of 2 points or more on the MADRS may be clinically relevant [Pilot trials are not primarily interested in treatment effect or efficacy. Indeed, according to the CONSORT statement (extension to randomized pilot and feasibility trials), formal hypothesis testing for effectiveness is not recommended in a pilot trial [The future full-scale RCT should avoid sources of bias that might influence the estimation of treatment effect, including selection or attrition bias. Fortunately, our pilot findings indicate that this is highly likely.The limitations of the study include the low proportion of MetS participants and lack of full data completeness regarding self-assessment questionnaires; however, these will be addressed in the future definitive RCT. Additionally, it was not possible to fully evaluate the tertiary outcome measures due to the small number of participants meeting the criteria for MetS. Nonetheless, it was not a primary or even secondary aim of this pilot study. The study also has some important strengths, mainly the high levels of acceptability, good retention ratio, and the detailed description of enrolled participants. Another strength is its selection of outcome measures, which covers several potential areas of probiotic action.