The Role of Probiotics in Mental Health: A randomised controlled trial among pregnant women with obesity in the Counties Manukau Health region, South Auckland

Abstract

Background: The experience of maternal mental health issues such as perinatal depression and anxiety, has been associated with a myriad of adverse consequences for mothers, their offspring, and the wider family. Maternal obesity represents an additional significant and prevalent health condition associated with adverse pregnancy and longer-term outcomes, that has been identified as a factor contributing to an increased risk of maternal mental health issues. In the Counties Manukau Health (CMH) region in South Auckland, New Zealand, there is a high percentage of women entering pregnancy with obesity. In addition, a significant proportion of pregnant women in the CMH region experience high levels of socioeconomic deprivation and belong to ethnic minority groups, potentially increasing the vulnerability of these women to experiencing maternal mental health issues. Emerging research suggests that probiotics may represent a novel means by which to target mental health issues and obesity, via manipulation of the gut microbiota and the gut-brain axis. No studies have yet explored the effects of probiotics on mental health outcomes within the context of maternal obesity. Aim: This study was conducted to investigate the influence of probiotic capsules on mental health outcomes among a multi-ethnic sample of pregnant women with obesity residing in the CMH region in South Auckland, New Zealand. The study also aimed to examine the rate of depression in late pregnancy within this sample, and to explore body mass index (BMI), history of depression, deprivation, and ethnicity as contributory risk factors for depression. Methods: The current study was conducted as a sub-study of the larger Healthy Mums and Babies (HUMBA) trial, a single-centre two-by-two factorial randomised controlled demonstration trial (parallel groups). A total of 230 pregnant women with obesity (BMI ≥30.0 kg/m2) were recruited from within the CMH region between April 2015 and June 2017, and randomised to receive either probiotic or placebo capsules (double-blind), in addition to a dietary intervention or routine dietary advice (no blinding). The probiotic capsules contained Lactobacillus rhamnosus GG and Bifidobacterium lactis BB12 (Chr. Hansen A/S, Hoersholm, Denmark), at a dose of 6.5 x 109 colony forming units (cfu) per day. Maternal mental health outcomes of depression, anxiety, and functional health and well-being were assessed at baseline (120-176 weeks' gestation) and 36 weeks of pregnancy. Primary outcome data (depression scores at 36 weeks of pregnancy) were obtained for a total of 164 women. Results: Analyses revealed that the probiotics did not significantly improve depression, anxiety, or functional health and well-being scores from baseline to 36 weeks of pregnancy within the sample. Depression scores remained stable across the two time points, and did not differ between the probiotic intervention and the placebo control groups. Anxiety scores increased (i.e. worsened) over time, irrespective of group allocation. Physical well-being scores decreased (i.e. worsened) over time irrespective of group allocation, and mental well-being scores did not differ between the two groups at 36 weeks of pregnancy. In terms of risk factors, BMI, history of depression, deprivation, and ethnicity, were not found to be associated with depression scores at 36 weeks of pregnancy. The rate of depression in the sample at 36 weeks of pregnancy was 10%. Conclusion: No beneficial effects of Lactobacillus rhamnosus GG and Bifidobacterium lactis BB12 on mental health outcomes were observed in this sample, and thus the use of probiotics for mental health benefits cannot yet be recommended for pregnant women with obesity. Probiotic research is, however, at an emergent stage, and further studies are required to validate and build on these findings. This study has highlighted the need for more human randomised controlled trials to help elucidate the effective components of probiotic interventions for mental health benefits for different populations. Specifically, research is needed to investigate the optimal strain, dosage, duration, and timing of probiotic interventions, in addition to the possible mechanistic pathways underpinning these components. This will facilitate future clinical applications of probiotics and improve theoretical understanding of the gut-brain axis. This study has provided a unique contribution to the literature on probiotics and mental health, and has contributed towards addressing a significant research gap by exploring this notion within the context of a highly deprived, multi-ethnic New Zealand sample of pregnant women with obesity.