3.4. Lifestyle Behaviors Interact with Probiotic Effects
As the HB pattern showed significant associations with mental health, further analyses were conducted on this aspect. We had previously hypothesized that the effects of the probiotic could be associated with lifestyle patterns of the participants. To explore this association, we generated a separate mixed-effect model for each one of the psychological variables. Each model included as a fixed effect the subject score of healthy behaviors (HB), time (baseline, post, and follow-up), treatment group (probiotic/placebo) and the three-way and two-way interactions between these variables. Subjects were included as a random effect. In each model, we also controlled for age and gender.Our parameters of interest were the interaction between treatment groups, lifestyle habits, and time. This three-way interaction reflects how the relationship between variables changes across time. Since there is not a clear view of the effect of probiotics on psychological outcomes [We first analyzed whether health behavior interacted with the effects of probiotic treatment in predicting change between the baseline and the post-treatment time. The estimate of this three-way interaction is shown in We later analyzed whether health behavior interacted with the probiotic in predicting change between the baseline and the follow-up time. The estimate of this three-way interaction can be seen in Collectively, these results suggest that lifestyle habits should be considered when assessing the positive impact of a probiotic formulation on well-being and mental process. Alternatively, the adoption of healthier lifestyle habits could be included by design alongside probiotic intake. Importantly, as observed in this population, some beneficial effects might be masked if considering all participants together, especially when studying general population samples considered as otherwise healthy.