Saliva Bacteria Can Help Predict Suicidal Thoughts

Tiny organisms living in our mouths could hold clues about our mental well-being. Bacteria found in the saliva of individuals who have suicidal thoughts are different than those who don’t. This groundbreaking discovery about the connection can help provide mental health assistance for suicidal ideation and save lives.

Researchers at the University of Florida have found that bacteria in the saliva of college students who reported recent thoughts of suicide differed significantly from those found in students who had not experienced recent suicidal thinking.

This was the first study to look at bacterial differences in the saliva of those with and without recent suicidal ideation (suicidal thoughts). As part of the research suicidal ideation is defined as thoughts of suicide within the two weeks before the saliva sample was taken.

Students with suicidal thoughts have higher levels of bacteria associated with periodontal disease

The researchers discovered that students with recent suicidal thoughts had greater levels of bacteria associated with periodontal disease and other inflammatory health disorders after controlling for the influence of other factors known to affect mental health, such as food and sleep.

They also discovered that the bacteria Alloprevotella rava, which is known to create a chemical that supports brain health, was present at lower levels in these adolescents. Additionally, the researchers discovered that these students had a genetic difference that might affect the amount of Alloprevotella rava in the mouth.

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

To predict suicidal ideation based on a person’s microbiome

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

The study examined saliva obtained from roughly 500 undergraduate students enrolled in courses offered by the UF Department of Microbiology and Cell Science. Additionally, these students filled out the Patient Health Questionnaire-9, which is used to check for signs of depression and inquire about recent suicidal thoughts. People who disclosed having recently considered suicide were sent to the campus’s mental health facilities.

“Mental health and suicide are serious issues on college campuses, and our students were very interested in being a part of research that can help address this problem. We are continuing to collect data for follow-up studies and hope more students and universities will become involved,” said Eric Triplett, chair of the microbiology and cell science department and senior author of the study.

Up to 25% of people between the ages of 18 to 24 seriously thought about suicide

In college-aged adults, depression and suicide ideation are relatively common: According to a CDC report from 2020, up to 25 percent of individuals between the ages of 18 and 24 had considered suicide seriously within the previous month.

Initially, participants had to bring a saliva sample to the lab for this study, but now they can choose to send their saliva sample by mail using a collection kit created by the researchers.

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

“While various treatments and lifestyle changes can help, there is still much to be learned about how the human microbiome affects mental health and could be harnessed to improve it,” Ahrens said.

Story Source:

Materials provided by the University of Florida. Original written by Samantha Murray. Note: Content may be edited for style and length.

Journal Reference:

Angelica P. Ahrens, Diego E. Sanchez-Padilla, Jennifer C. Drew, Monika W. Oli, Luiz F. W. Roesch, Eric W. Triplett. Saliva microbiome, dietary, and genetic markers are associated with suicidal ideation in university students. Scientific Reports, 2022; 12 (1) DOI: 10.1038/s41598-022-18020-2

Page citation:

University of Florida. “Study uncovers differences in saliva bacteria of students with recent suicidal thoughts.” ScienceDaily. ScienceDaily, 25 August 2022. <>.

Help is here:

Toll-Free Mental Health Rehabilitation Helpline Kiran (1800-599-0019)

Name of the Organisation: Vandrevala Foundation

Vandrevala Foundation is a non-profit that partners with organizations to help communities thrive by providing education and healthcare. Vandrevala Foundation launched a mental health helpline in India in 2009 to offer free psychological counselling and crisis mediation to anyone who is experiencing distress due to depression, trauma, mood disorders, chronic illness, and relationship conflict.


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