Lee, S.-H., Ku, X., Oh, H.-S., Jung, Y., Chun, J., & Choi, I. (2024). Longitudinal associations between gut microbiome diversity and emotional well-being. Health Psychology, 43(5), 323–327. https://doi.org/10.1037/hea0001350
Key Points
- The study found significant positive cross-sectional associations between emotional well-being (EWB) and gut microbiome diversity (measured by the Shannon Index, SI) in both 2019 and 2022.
- However, no significant longitudinal associations were found between 2019 EWB and 2022 SI, or between 2019 SI and 2022 EWB.
- The findings suggest that while emotional happiness may be associated with gut microbiome profiles at a particular time point, they may not serve as predictive factors for each other over time.
- Further research is needed to establish causal relationships between EWB and gut microbiome diversity, as well as to explore potential mediating factors such as diet and nutrition.
- The study highlights the complex and multifaceted relationship between mental well-being and gut health, underscoring the importance of continued research in this area.
Rationale
Recent studies have reported a significant link between emotional well-being (EWB) and the gut microbiome (Lee et al., 2020; Simpson et al., 2021; Valles-Colomer et al., 2019).
However, the temporal dynamics of this relationship have not been well-established, with a notable scarcity of longitudinal study designs examining microbiome dynamics (Björk et al., 2019).
To address this gap, the present study aimed to investigate the longitudinal associations between EWB and gut microbiome diversity, specifically using the Shannon Index (SI) as a measure of alpha diversity.
By employing a cross-lagged panel design, the researchers sought to discern potential causal effects over time, contributing to a more comprehensive understanding of the gut-brain axis.
Method
The study utilized a longitudinal cross-lagged panel design, assessing participants’ EWB and gut microbiome diversity (measured by SI) at two time points: 2019 and 2022.
Procedure
Participants were recruited from the panels of the Korean Longitudinal Aging Study. In 2019, a subsample of participants agreed to submit stool samples for gut microbiome analysis and undergo psychological assessments.
In 2022, a subset of these participants agreed to submit stool samples again and respond to psychological surveys.
Sample
The final sample consisted of 57 participants who took part in both the 2019 and 2022 data collection (56.1% female, mean age = 52.47 years, SD = 12.65, range = 27–73 as of 2022).
Measures
- EWB was assessed using the 20-item Positive Affect and Negative Affect Schedule (PANAS).
- Gut microbiome profiles were generated by sequencing the 16S rRNA gene from fecal samples, and the Shannon Index (SI) was calculated as a measure of alpha diversity.
Statistical measures
A cross-lagged panel model was used to test the reciprocal longitudinal effects between EWB and SI, controlling for age and gender. The model was analyzed using Mplus 7.4.
Results
- There was a significant autoregressive effect for emotional well-being (EWB), but not for gut microbiome diversity (measured by the Shannon Index, SI).
- No significant longitudinal associations were found between EWB and SI in either direction.
- Significant cross-sectional associations were found between EWB and SI in both 2019 and 2022.
Insight
This study provides valuable insights into the temporal dynamics of the relationship between emotional well-being and gut microbiome diversity.
An individual’s emotional well-being (EWB) at one point in time was significantly related to their EWB at a later point in time. In other words, a person’s current level of emotional well-being was predictive of their future emotional well-being.
However, the same was not true for gut microbiome diversity, as measured by the Shannon Index (SI). The diversity of an individual’s gut microbiome at one point in time was not significantly related to the diversity of their gut microbiome at a later point in time.
This suggests that gut microbiome diversity may be more variable over time and less predictable based on past measurements, compared to emotional well-being.
While previous research has established cross-sectional associations between these factors (Lee et al., 2020), the current findings suggest that EWB and SI may not reliably predict each other over time.
The observed cross-sectional associations in both 2019 and 2022 support the notion that individuals’ gut microbiome diversity may be highly susceptible to their emotional states, potentially serving as a biological indicator of state-level psychological attributes rather than chronic-level traits.
Future research should explore the role of dietary alterations resulting from different emotional states in shaping microbiome diversity and investigate other indices of gut microbiome composition beyond the Shannon Index.
Strengths
- A longitudinal design with two time points, allowing for the examination of temporal relationships between EWB and SI.
- The use of a cross-lagged panel model to discern potential causal effects over time.
- The assessment of both psychological (EWB) and biological (SI) measures, providing a comprehensive approach to the gut-brain axis.
Limitations
- The small sample size (N = 57) and relatively long interval between measurements (3 years) may not fully capture the complexity of the relationships between EWB and SI.
- The study focused primarily on the Shannon Index as a measure of gut microbiome diversity; future research should investigate other indices of gut microbiome composition.
- The sample was drawn from a specific population (Korean adults), which may limit the generalizability of the findings to other populations.
ClinicalImplications
The results of this study have important implications for understanding the complex relationship between emotional well-being and gut health.
While the findings do not support a reliable longitudinal association between EWB and SI, they highlight the potential for short-term, state-level interactions between these factors.
Nutrition may play a mediating role between EWB and gut microbiome diversity, as emotional states are linked to eating behaviors. Psychological stress and depression can increase consumption of high-fat and high-sugar foods, influencing gut microbiome composition.
A healthy diet, particularly a plant-based one rich in berries and green leafy vegetables, has been proposed as an intervention therapy for psychiatric disorders. This highlights the crucial role of diet in shaping the gut microbiome and promoting brain-gut communication. Probiotics and prebiotics have also been implicated in enhancing mental well-being.
When considering these findings alongside other psychological factors such as personality, loneliness, and stress, which have been associated with variations in gut microbiome composition, it is plausible that dietary changes resulting from different emotional states could potentially impact microbiome diversity.
This underscores the need for further research to elucidate the mechanisms underlying the gut-brain axis, including the role of diet and nutrition as potential mediators.
The study also emphasizes the importance of considering both psychological and biological factors in the context of mental health and well-being, as well as the need for continued research to establish causal relationships between these variables.
References
Primary reference
Lee, S.-H., Ku, X., Oh, H.-S., Jung, Y., Chun, J., & Choi, I. (2024). Longitudinal associations between gut microbiome diversity and emotional well-being. Health Psychology, 43(5), 323–327. https://doi.org/10.1037/hea0001350
Other references
Björk, J. R., Dasari, M., Grieneisen, L., & Archie, E. A. (2019). Primate microbiomes over time: Longitudinal answers to standing questions in microbiome research. American Journal of Primatology, 81(10–11), Article e22970. https://doi.org/10.1002/ajp.22970
Lee, S. H., Yoon, S. H., Jung, Y., Kim, N., Min, U., Chun, J., & Choi, I. (2020). Emotional well-being and gut microbiome profiles by enterotype. Scientific Reports, 10(1), Article 20736. https://doi.org/10.1038/s41598-020-77673-z
Simpson, C. A., Diaz-Arteche, C., Eliby, D., Schwartz, O. S., Simmons, J. G., & Cowan, C. S. (2021). The gut microbiota in anxiety and depression–a systematic review. Clinical Psychology Review, 83, Article 101943. https://doi.org/10.1016/j.cpr.2020.101943
Valles-Colomer, M., Falony, G., Darzi, Y., Tigchelaar, E. F., Wang, J., Tito, R. Y., Schiweck, C., Kurilshikov, A., Joossens, M., Wijmenga, C., Claes, S., Oudenhove, L. V., Zhernakova, A., Vieira-Silva, S., & Raes, J. (2019). The neuroactive potential of the human gut microbiota in quality of life and depression. Nature Microbiology, 4(4), 623–632. https://doi.org/10.1038/s41564-018-0337-x
