Non-invasive Saliva Test Detects Patients with Post-traumatic Stress Disorder

A recent paper described a noninvasive saliva-based test that uses RNA sequencing to detect changes in the oral microbiome that can identify individuals suffering from post-traumatic stress disorder (PTSD).

The symptoms of PTSD include intrusiveness (involuntary nightmares or flashbacks), avoidance of traumatic memories, negative alterations in cognition and mood (such as negative beliefs about oneself or social detachment), increased arousal and reactivity with irritable reckless behavior, concentration problems, and sleep disturbances. PTSD is also closely linked to anxiety, depression, and substance abuse.

Investigators at Tel Aviv University (Israe) and Haifa University (Israel) conducted a study to determine whether PTSD diagnosis could be changed from subjective, self-reported psychological measurements to objective molecular biomarkers.

For this study, they worked with a unique cohort of 200 Israeli veterans who had participated in the 1982 Lebanon war. The participants were assessed for various psychological aspects, including sleep, appetite disorders, guilt, suicidal thoughts, social and spousal support, hostility, satisfaction with life, as well as issues of demographics, psychopathology, welfare, health, and education.

The investigators collected saliva samples from the participants and compared the results of the subjects' microbial distribution to the psychological results and their responses to the welfare questionnaires.

Results revealed a microbiota signature (i.e., decreased levels of the bacteria sp_HMT_914, 332 and 871 and Noxia) that was correlated with PTSD severity. In contrast, education duration correlated with significantly increased levels of sp_HMT_871 and decreased levels of Bacteroidetes and Firmicutes.

In the gastrointestinal microbiota Bacteroidetes (also known as Bacteroidota) have a very broad metabolic potential and are regarded as one of the most stable part of gastrointestinal microflora. Reduced abundance of the Bacteroidota in some cases is associated with obesity. This bacterial group appears to be enriched in patients with irritable bowel syndrome and involved in type I and type II diabetes).

Firmicutes (also known as Bacillota) make up about 30% of the mouse and human gut microbiome. The phylum Bacillota as part of the gut microbiota has been shown to be involved in energy resorption, and potentially related to the development of diabetes and obesity. Within the gut of healthy human adults, the most abundant bacterium: Faecalibacterium prausnitzii, which makes up 5% of the total gut microbiome, is a member of the Bacillota phylum).

Air pollution was positively correlated with PTSD symptoms, psychopathological symptoms, and microbiota composition. Arousal and reactivity symptoms were correlated with reductions in transaldolase, an enzyme controlling a major cellular energy pathway, that potentially accelerates aging.

"To the best of our knowledge, this is the first depiction of a microbial signature in the saliva among veteran soldiers with PTSD," said senior author Dr. Illana Gozes, professor of molecular genetics biochemistry at Tel Aviv University. "We were surprised to discover that about a third of the PTSD subjects had never been diagnosed with post-trauma, so they never received any recognition from the Ministry of Defense and the official authorities. To the best of our knowledge, this is the first depiction of a microbial signature in the saliva among veteran soldiers with PTSD. It must be stressed that until now, post-trauma diagnosis has been based solely on psychological and psychiatric measures. Thanks to this study, it may be possible, in the future, to use objective molecular and biological characteristics to distinguish PSTD sufferers, taking into account environmental influences. We hope that this new discovery and the microbial signatures described in this study might promote easier diagnosis of post-traumatic veteran soldiers so they can receive appropriate treatment."

The study was published in the July 22, 2022, online edition of the journal Molecular Psychiatry.