Having suicidal thoughts changes saliva, study shows

GAINESVILLE, Fla. — They say you are what you eat, but perhaps the saying should go you are what you think. Fascinating new research from the University of Florida uncovers a connection between our thoughts and physical, bacterial changes in saliva. Scientists report that bacteria in the saliva of college students who reported recent thoughts of suicide differed significantly in comparison to the saliva of other students.

While modern science is beginning to focus more on mental health’s impact on the human microbiome, this is the first study to specifically investigate bacterial differences in the saliva of those with and without recent suicidal thoughts. Recent suicidal thoughts, also called suicidal ideation, is defined by researchers as any thoughts of suicide within the two weeks prior to saliva sample collection.

After accounting for the potential influence of various other factors known to impact mental health (diet, sleep, etc), scientists report that students with recent suicidal thoughts displayed higher levels of a particular bacteria associated with gum disease and other inflammatory health issues.

Moreover, students who had recently experienced suicidal ideation also had lower levels of Alloprevotella rava, which is a bacterium known to promote robust brain health. Those same students also shared a a genetic variation that researchers explain may influence oral A. rava levels.

“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 affects mental health?” says first study author Angelica Ahrens, postdoctoral researcher in the UF/IFAS microbiology and cell science department, in a university release. “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,”

These conclusions are based on saliva samples taken from close to 500 undergraduate students enrolled in in the microbiology and cell science department at the University of Florida. Subjects also filled out a survey commonly used to screen for depression symptoms. The questionnaire also asks respondents if they’d any thoughts of suicide within the last two weeks. Any students who did report recent suicidal ideation were referred to on-campus mental health services.

“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,” adds senior study author Eric Triplett, chair of the microbiology and cell science department.

Both depression and suicidal ideation are troublingly common among college-aged individuals. According to a 2020 study by the CDC, up to 25 percent of people aged 18 through 24 had seriously contemplated suicide within the last month.

While students had to physically visit the campus lab to provide a saliva sample for this study, moving forward study authors say participants can opt to send in their saliva sample by mail via a new collection kit recently designed by the research team. “This at-home method is very convenient for students and also 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 explains. “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,” she concludes.

The study is published in Scientific Reports.

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