Depression is a global mental health issue, particularly affecting adolescents and young adults. While the role of gut microbiota in depression has been extensively studied, the influence of the oral microbiome remains underexplored. Recent studies suggest that the oral microbiome may affect systemic and brain health through the oral-brain axis. This study aimed to investigate the relationship between oral microbiome diversity and depression using data from 6212 participants in the National Health and Nutrition Examination Survey (NHANES) 2009-2012.

Oral microbiome diversity was assessed through oral rinse samples using 16S rRNA sequencing, focusing on α-diversity metrics (observed ASVs and Faith's phylogenetic diversity) and β-diversity measures. Depressive symptoms were evaluated with the Patient Health Questionnaire (PHQ-9). Weighted logistic regression models were employed to assess associations between α-diversity and depression, while linear regression was used to examine the relationship between α-diversity and PHQ-9 scores. β-diversity differences were analyzed via permutational analysis of variance (PERMANOVA).

10.03% of the participants were diagnosed with depression. Higher α-diversity in the oral microbiome was negatively correlated with depression: observed ASVs (OR: 0.713 [CI: 0.508-0.999], P = 0.050) and Faith's phylogenetic diversity (OR: 0.584 [CI: 0.367-0.931], P = 0.025). Linear regression indicated that greater α-diversity was associated with lower PHQ-9 scores, reflecting fewer depressive symptoms. Furthermore, β-diversity analysis revealed significant differences in the microbiome composition between depressed and non-depressed individuals.

Reduced oral microbiome diversity is associated with an increased risk and severity of depression. The study underscores the importance of exploring the oral-brain axis and highlights the need for further research into the mechanisms and therapeutic strategies targeting this relationship.

Psychological stress is a potential modifiable environmental risk factor causally related to the exacerbation of periodontitis and other chronic inflammatory diseases. This animal study aimed to investigate comprehensively the preventive efficacy of systemic melatonin administration on the possible effects of restraint stress on the periodontal structures of rats with periodontitis.

Forty-eight male Sprague Dawley rats were randomly divided into six groups: control, restraint stress (S), S-melatonin (S-Mel), experimental periodontitis (Ep), S-Ep, and S-Ep-Mel. Periodontitis was induced by placing a 3.0 silk suture in a sub-paramarginal position around the cervix of the right and left lower first molars of the rats and keeping the suture in place for 5 weeks. Restraint stress was applied simultaneously by ligation. Melatonin and carriers were administered to the control, S, Ep, and S-Ep groups intraperitoneally (10 mg/body weight/day, 14 days) starting on day 21 following ligation and subjection to restraint stress. An open field test was performed on all groups on day 35 of the study. Periodontal bone loss was measured via histological sections. Histomorphometric and immunohistochemical (RANKL and OPG) evaluations were performed on right mandibular tissue samples and biochemical (TOS (total oxidant status), TAS (total antioxidant status), OSI (oxidative stress index), IL-1β, IL-10, and IL-1β/IL-10) evaluations were performed on left mandibular tissue samples.

Melatonin significantly limited serum corticosterone elevation related to restraint stress (p < .05). Restraint stress aggravated alveolar bone loss in rats with periodontitis, while systemic melatonin administration significantly reduced stress-related periodontal bone loss. According to the biochemical analyses, melatonin significantly lowered IL-1β/IL-10, OSI (TOS/TAS), and RANKL/OPG rates, which were significantly elevated in the S-Ep group.

Melatonin can significantly prevent the limited destructive effects of stress on periodontal tissues by suppressing RANKL-related osteoclastogenesis and oxidative stress.

Periodontitis is a chronic oral disease caused by pathogenic microorganisms that corrode tooth tissue, form periodontal pockets, absorb alveolar bone, and finally lead to tooth loss. During treatment, patients are prone to anxiety, tension, and other negative emotions, which affect their ability to face the disease and may also lead to aggravation of the original condition and affect oral health. Therefore, it is important to improve the negative psychology of patients with periodontitis to clarify the factors that may lead to negative psychological emotions.

To investigate the risk factors that may lead to anxiety and depression in patients with periodontitis.

One hundred patients with periodontitis were selected between March 2022 and March 2023 at our hospital. All patients were assessed with the Zung Self-rating Depression Scale (SDS) (≥ 53 points indicate a depressive state) and Zung Self-rating Anxiety Scale (SAS) (≥ 50 points indicates an anxious state). In this study, patients who experienced anxiety or depression were included in the occurrence group and those without anxiety or depression were included in the non-occurrence group. The baseline data of the two groups were compared to explore the risk factors for anxiety and depression in patients with periodontitis.

A total of 100 patients with periodontitis were included in this study. According to the SDS, 38 patients (38.00%) developed depression, with an average SDS score of (68.52 ± 5.85) points. According to the SAS, 40 patients (40.00%) developed anxiety, and the average SAS score was (72.15 ± 4.15) points. In this study, 56 patients with anxiety or depression were included. Compared with the non-occurrence group, the occurrence group had higher ages (≥ 60 years), lower level of hope (low level), educational level (high school or below), disease perception (poor), and sleep disorder (yes). The negative coping dimension scores of the simplified coping style questionnaire (SCSQ) and Dental Fear Scale (DFS) in the occurrence group were higher, whereas the score of the positive coping dimension of the SCSQ was significantly lower (P < 0.05). There were no significant differences in the other data between the groups (P > 0.05). The results of multiple logistics regression analysis showed that age (≥ 60 years), level of hope (low level), educational level (high school or below), disease perception (poor), sleep disorder (yes), high negative coping dimension scores of SCSQ, high score of DFS, and low positive coping dimension scores of SCSQ were all factors contributing to the anxiety and depression in patients with periodontitis (odds ratio > 1, P < 0.05).

Age, hope level, educational level, disease perception, sleep disorders, coping style, and dental fear were all associated with anxiety and depression in patients with periodontitis.

Stress is a physiological response of the body to stressful life events but may not be when the individual is persistently exposed to the stress trigger, and it negatively affects certain physiological functions, thus triggering psychosomatic diseases. In literature, chronic stress and inadequate coping strategies are found to mediate the risk and development of periodontitis; mechanisms have therefore been proposed to explain the effects of stress on the periodontium. Since stress is a prevalent problem in modern life and given the importance of maintaining oral health, the present literature review aimed to estimate the association between stress and periodontal disease. The research question adopted is the following: "Are psychological stress and periodontal disease related?" The search was conducted in August 2022 and limited to articles in electronic databases from 2017 to 2022 in English, excluding reviews and literature reviews. From the electronic databases, a total of 532 articles were identified and became 306 after reviews and duplicates were removed. An additional bibliographic search was conducted through the same electronic databases, controlled terms and keywords including only systematic reviews, which were previously excluded. Through the bibliography cited in the systematic reviews, an additional 18 articles were identified, with a new total of 324. As a result of reading the title and abstract of these 324 articles, an additional 295 were excluded. Reading the full text of the remaining 29 studies, 2 articles were excluded due to non-adherence to the eligibility criteria. The remaining 27 results were included in our literature review. It has been suggested in the literature that adverse socioeconomic conditions elicit a stress response, which can trigger periodontal inflammation. Most of the 27 articles included in the study confirm and demonstrate a positive association between psychological stress and periodontal disease. Numerous studies have shown the mechanisms through which chronic stress negatively affects periodontal tissues. Therefore, in the light of the results obtained from this review, it is important that oral health professionals, also for general health purposes, consider stress factors among the risk factors of periodontal disease, its severity and decreased efficacy of treatments. It is therefore advisable to act preventively through the interception of chronic stress.