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Experiencing symptoms of anxiety, depression, and Attention Deficit Hyperactivity Disorder (ADHD) simultaneously is common, suggesting shared underlying mechanisms. These mechanisms include dysregulation of neurotransmitters like dopamine and serotonin, structural and functional brain abnormalities in regions such as the prefrontal cortex and amygdala, genetic predispositions and environmental stressors.
One potential environmental contributor to psychiatric symptoms is the gut microbiota, the community of bacteria in our intestines. Previous studies have shown that changes in gut microbiota diversity are linked to various psychiatric conditions. However, no single type of gut bacteria is consistently associated with a specific condition, indicating that the association of the gut microbiome with mental health transcends individual diagnoses and should be studied across multiple disorders.
Researchers Danique Mulder and colleagues explored whether gut microbiome associations with psychiatric symptoms occur across disorders, focusing on stress-related (depression, anxiety) and neurodevelopmental (ADHD, autism spectrum disorder) disorders. The study, led by Alejandro Arias Vasquez, the principal investigator of the Brain, Bacteria & Behaviour (B3) group at Radboudumc, in collaboration with the departments of Psychiatry and Human Genetics, was published in Brain, Behavior, and Immunity on June 12, 2024.
Building on The MIND-Set Project at the Department of Psychiatry at Radboudumc, researchers used four symptom domains to capture different aspects of brain function and behavior in stress-related and neurodevelopmental disorders. For example, the "negative valence" domain reflects depressive and anxiety symptoms. They linked symptom severity in each domain to the abundance of different gut bacterial groups (genera) in stool samples.
The study demonstrates associations between the gut microbiota and domains of functioning across people with psychiatric conditions and unaffected individuals, potentially mediated by immune-related processes. These findings open possibilities for personalized treatments targeting the gut microbiota via nutritional interventions.
The researchers identified eight genera significantly associated with the symptom domains. For instance, lower levels of a genus called Clostridium Sensu Stricto 1 were found in people with more severe negative valence symptoms, regardless of comorbid conditions or medication use. Most of the eight associated genera have been linked to psychiatric disorders before. Interestingly, these genera were also reported in immune-mediated inflammatory diseases like Crohn’s Disease and Multiple Sclerosis. Some bacterial groups, like Clostridium Sensu Stricto 1 and Oscillibacter, seem involved in regulating gut barrier functioning, suggesting that changes in gut microbiota might influence psychiatric symptoms through effects on the gut barrier and inflammation.
The next steps for researchers include obtaining a more detailed picture of how these bacteria function and their link to immune activation. They will also explore the potential therapeutic uses of these bacteria, aiming to develop new ways to improve mental health through the gut microbiome.
Read the study here:
Mulder D, Jakobi B, Shi Y, Mulders P, Kist JD, Collard RM, Vrijsen JN, van Eijndhoven P, Tendolkar I, Bloemendaal M, Arias Vasquez A. Gut microbiota composition links to variation in functional domains across psychiatric disorders. Brain, Behavior, and Immunity. 2024 May; 120:275-287. doi:10.1016/j.bbi.2024.05.037. PMID: 38815661.
