Differences in salivary bacteria of students with recent suicidal thoughts

Overview: Students who reported recent suicidal thoughts had a different bacterial composition in their saliva than those who did not report suicidal thoughts. Notably, suicidal college students presented lower levels of Alloprevotella rava, a bacterium associated with positive brain health, in their saliva samples.

Source: University of Florida

A new study from the University of Florida has found that bacteria in the saliva of students who reported recent suicidal thoughts differed in significant ways from the bacteria found in students who had not recently experienced suicidal thoughts.

While there is a growing body of research on mental health and the human microbiome, this is the first study to look at bacterial differences in the saliva of people with and without recent suicidal thoughts, also known as suicidal thoughts. Recent suicidal thoughts were defined as suicidal thoughts within two weeks before the saliva sample was taken.

By controlling for the influence of other factors known to affect mental health, such as diet and sleep, the researchers found that students with recent suicidal thoughts had higher levels of bacteria linked to periodontitis and other inflammatory health conditions.

They also found that these students had lower levels of Alloprevotella rava, a bacterium known to produce a compound that promotes brain health. These students also shared a genetic variation that the researchers found may influence the presence of Alloprevotella rava in the mouth.

“These results are exciting because they tell us which bacteria to take a closer look at. Our question now is: what are these bacteria doing biologically that affects mental health?” said Angelica Ahrens, lead author of the study and a postdoctoral researcher in the department of microbiology and cell sciences at UF/IFAS. Ahrens led the study as part of her doctoral program at the UF/IFAS College of Agricultural and Life Sciences.

“Ultimately, we hope this line of research can help predict suicidal ideation based on a person’s microbiome and inform pro- or prebiotic treatments for those at risk,” Ahrens said.

The study analyzed saliva collected from nearly 500 undergraduate students taking classes in UF’s department of microbiology and cell science. These students also completed the Patient Health Questionnaire-9, which is used to screen for depression symptoms and asks respondents to tell them if they’ve had suicidal thoughts in the past two weeks. Those who reported recent suicidal thoughts were referred to on-campus mental health services.

“Mental health and suicide are serious issues on college campuses, and our students have been very interested in being part of research that can help address this issue. We continue to collect data for follow-up studies and hope that more students and universities will be involved,” said Eric Triplett, chair of the division of microbiology and cell sciences and senior author of the study.

This shows a depressed looking lady
They also found that these students had lower levels of Alloprevotella rava, a bacterium known to produce a compound that promotes brain health. Image is in the public domain

Depression and suicidal ideation are relatively common in college-age adults: A 2020 study from the CDC found that up to a quarter of people between the ages of 18 and 24 had seriously considered suicide in the past month.

For this first study, students came to the lab to provide a saliva sample, but today participants can choose to send their saliva sample in the mail using a collection kit developed by the researchers.

“This at-home method is very useful for students and also helps us build a more diverse dataset and test different variables. For example, we want to look at the saliva microbiome of people who have been diagnosed with depression and who are taking antidepressants,” says Ahrens.

“While various treatments and lifestyle changes can help, there is still a lot to learn about how the human microbiome affects mental health and can be used to improve it,” Ahrens said.

About this microbiome and mental health research news

Author: press office
Source: University of Florida
Contact: Press Office – University of Florida
Image: The image is in the public domain

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Original research: Open access.
“Saliva microbiome, nutritional and genetic markers are associated with suicidal ideation in college students” by Angelica P. Ahrens et al. Scientific Reports


Abstract

Salivary microbiome, nutritional and genetic markers are associated with suicidal thoughts in college students

Here, salivary microbiota and major histocompatibility complex (MHC) human leukocyte antigen (HLA) alleles were compared between 47 (12.6%) young adults with recent suicidal ideation (SI) and 325 (87.4%) controls without recent SI. Several bacterial taxa were correlated with SI after controlling for sleep problems, diet and genetics.

Four MHC class II alleles were protective for SI, including DRB1*04, which was absent in all subjects with SI, while it was present in 21.7% of controls. An increased incidence of SI was observed in four other MHC class II alleles and two MHC class I alleles.

Associations between these HLA alleles and salivary bacteria were also identified. In addition, rs10437629, previously associated with suicide attempt, was correlated here with SI and the absence of Alloprevotella ravaa producer of an organic acid known to promote brain energy homeostasis.

Therefore, microbial-genetic associations may be important players in the diathesis-stress model for suicidal behavior.

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