Microbiome in saliva linked to suicidal ideation in university students

Suicide is the second leading cause of death in individuals between the ages of 10–34 in the United States. Worldwide life-time prevalence of suicidal ideation (SI) was estimated to be 9.2% in a 2008 report of suicidal behaviors in 84,850 adults across 17 countries2. In a study of 67,000 degree-seeking college students across 108 institutions, 16,337 (24.3%) reported they harbored SI and 9.3% had made a suicide attempt3. The strongest association with suicidality, self-injury, suicide attempts, and mental health diagnosis in students was exposure to stress, in a dose-dependent manner. Three or more exposures to stress resulted in 4.25 to 10.06 times higher endorsement of SI3, consistent with the diathesis-stress model of depression

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 issues, diet, and genetics.

Four MHC class II alleles were protective for SI including DRB1*04, which was absent in every subject with SI while present in 21.7% of controls.

The results:

• Increased incidence of SI was observed with four other MHC class II alleles and two MHC class I alleles.
• Associations between these HLA alleles and salivary bacteria were also identified.
• Furthermore, rs10437629, previously associated with attempted suicide, was correlated here with SI and the absence of Alloprevotella rava, a producer of an organic acid known to promote brain energy homeostasis.

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

Reference:

Ahrens AP, Sanchez-Padilla DE, Drew JC, Oli MW, Roesch LFW, Triplett EW. Saliva microbiome, dietary, and genetic markers are associated with suicidal ideation in university students. Sci Rep. 2022 Aug 22;12(1):14306. doi: 10.1038/s41598-022-18020-2. PMID: 35995968; PMCID: PMC9395396.

Keywords:

Ahrens AP, Sanchez-Padilla DE, Drew JC, Oli MW, Roesch LFW, Triplett EW, Saliva microbiome, dietary, genetic, markers, associated, suicidal, ideation, university, students, Scientific Reports