Humid Heat Causes Anxiety by Disrupting Gut Health and Bile Acid Processing

Jim Crocker
8th July, 2024

Humid Heat Causes Anxiety by Disrupting Gut Health and Bile Acid Processing

Image Source: Natural Science News, 2024

Key Findings

  • The study from Jinan University found that a humid heat environment causes anxiety-like behavior in male mice
  • This environment led to gut microbiota imbalance, specifically reducing Lactobacillus murinus and increasing harmful bile acids
  • The study suggests that probiotics could help treat anxiety disorders caused by environmental stressors
Climate change and its associated environmental changes pose significant threats to human mental health. However, understanding the specific environmental conditions that impact neuropsychiatric disorders has remained elusive. Recent research conducted by Jinan University sheds light on this issue by examining the effects of a humid heat environment on the brain and gut microbiota in male mice[1]. The study reveals that exposure to a humid heat environment can induce anxiety-like behavior in male mice. To understand the underlying mechanisms, the researchers performed microbial 16S rRNA sequencing analysis, which showed that this environment caused gut microbiota dysbiosis. Specifically, there was a decreased abundance of Lactobacillus murinus. Metabolomics further revealed an increase in serum levels of secondary bile acids, such as lithocholic acid. In addition to gut microbiota changes, the study found increased neuroinflammation, indicated by elevated levels of proinflammatory cytokines in the serum and cortex. This was accompanied by activated PI3K/AKT/NF-κB signaling and a microglial response in the cortex. Importantly, when the microbiota from mice reared in a humid heat environment was transplanted into germ-free mice, these abnormalities were replicated. Conversely, administering Lactobacillus murinus markedly reversed these abnormalities. The findings were not limited to mice. Human samples collected during the humid heat season also showed a decrease in Lactobacillus murinus abundance and an increase in serum lithocholic acid concentration. This suggests that gut microbiota dysbiosis induced by a humid heat environment drives the progression of anxiety disorders by impairing bile acid metabolism and enhancing neuroinflammation. The study proposes that probiotic administration could be a potential therapeutic strategy for these disorders. These findings align with previous research that has explored the prevalence and impact of anxiety disorders globally. For instance, a study using a Bayesian meta-regression approach reported that anxiety disorders are more common in regions with a history of recent conflict and high-income areas[2]. This suggests that environmental stressors, such as climate conditions, could exacerbate anxiety disorders in these regions. Additionally, the impact of weather on psychiatric conditions has been highlighted in studies examining the number of patients presenting in psychiatric emergency rooms. One study found that the number of patients was significantly higher in warmer and cloudier conditions, indicating that weather influences the number of psychiatric patients seeking emergency care[3]. Another study found that rising temperatures could positively affect mood in the general population but negatively impact individuals with anxiety, depression, and schizophrenia[4]. These findings suggest that certain environmental conditions, such as temperature and humidity, can have complex effects on mental health. The current study from Jinan University expands on these findings by providing a mechanistic understanding of how a humid heat environment can induce anxiety-like behavior through gut microbiota dysbiosis and neuroinflammation. This research underscores the importance of considering environmental factors in the management and treatment of anxiety disorders and highlights the potential of probiotics as a therapeutic intervention. In summary, the study conducted by Jinan University demonstrates that a humid heat environment can cause anxiety-like behavior in male mice through gut microbiota dysbiosis and neuroinflammation. These findings are supported by previous research on the prevalence and impact of anxiety disorders and the influence of weather on psychiatric conditions. The study suggests that probiotic administration could be a potential therapeutic strategy for anxiety disorders induced by environmental stressors.

EnvironmentMental HealthBiochem


Main Study

1) Humid heat environment causes anxiety-like disorder via impairing gut microbiota and bile acid metabolism in mice.

Published 7th July, 2024

Related Studies

2) The regional distribution of anxiety disorders: implications for the Global Burden of Disease Study, 2010.

3) Weather conditions influence the number of psychiatric emergency room patients.

4) How ambient temperature affects mood: an ecological momentary assessment study in Switzerland.

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