Willoughby D. Miller in 1891 was the first one who suggested that oral infection may lead to systemic diseases. Host health status also impacts the composition of mouth microorganisms. Oral microbiota refers to the diverse population of microorganisms that reside within the mouth ecosystem. This community includes various microorganisms, such as bacteria, fungi, and viruses, that inhabit the oral cavity. The mouth is the first part of the body that directly interacts with the environment; therefore, its microbiome population is very dynamic and influenced by environmental factors. Similar to other microbiomes which exist in gut and vagina, they play a major role in health and diseases. It has been shown that oral infections cause tooth and gum problems, cardiovascular diseases, inflammatory bowel disease, cancers, cardiovascular diseases, Alzheimer, diabetes, and rheumatoid arthritis.
Oral microbes and mental disease
Many research studies show that the gut microbiome impacts mental conditions through the gut-brain axis; however, fewer studies have been performed on the psychological roles of mouth microorganisms in humans. Since the oral microbiome is easily transmitted among people in social or romantic interactions, it is important to elucidate its influence on mental and physical health. Recent studies show a link between the bacteria in our mouths and mental health. Limited recent studies show a link between the bacteria in our mouths and mental health, suggesting that certain types of mouth bacteria might be connected to conditions like anxiety, depression, and post-traumatic stress disorder (PTSD). While scientists are still figuring out exactly how this works, the results hint that taking care of our oral health could be important for our mental well-being.
There is evidence showing that periodontal diseases and tooth loss in older individuals are correlated with cognitive impairment. It has been observed that P. gingivalis-induced gum infection increases amyloid plaque brain inflammation. Some studies also revealed that there is a strong relationship between irregular tooth brushing and Alzheimer’s disease. It should be noted that Alzheimer’s and periodontal diseases are multifactorial disorders, and common factors, including smoking or oral hygiene, impact both of them, so the oral microbiome may just be one risk factor in neurodegenerative diseases.
A new cohort study looked at how the bacteria in our mouths might be connected to mental health issues like anxiety, depression, and trauma, as well as gum disease. Researchers conducted a study involving a large group of people and found that those with certain mental health conditions exhibited distinct types of mou [1]th bacteria compared to healthier individuals. Specific bacteria, including Porphyromonas gingivalis (P. gingivalis) and Fusobacterium nucleatum, were linked to both mental health problems and gum disease, indicating a potential connection between oral health and brain health. The findings suggest that taking care of our oral health might also help our mental health, and more research is needed to understand this connection better and find potential treatments [2].
Romantic relationships may have the potential risk of transferring harmful microbes to the mouth
Social interactions, particularly romantic relationships, influence the composition of oral microorganisms through activities such as close conversation, kissing, and other sexual behaviors. Research indicates that approximately 80 million microbes can be transferred during a 10-second kiss [3]. Sharing oral microbiomes between partners can create similar oral bacteria populations, potentially posing health risks, especially for those with pre-existing conditions like gum infections or even physical and mental disorders. Let’s examine how romantic relationships might influence mental health through this connection.
First, mouth microbes influence more than just your teeth. If kissing introduces new bacteria—say, ones linked to gum disease like P gingivalis—it could increase inflammation in the body. Chronic inflammation leads to brain inflammation and is a known player in mental health conditions like depression and anxiety. For example, research has shown that people with periodontitis (severe gum disease) may have higher rates of depression, possibly because inflammatory molecules travel through the bloodstream and affect the brain.
Second, some microbes from the mouth can migrate to the gut, thereby altering its microbiome. It is well recognized that gut microbiota significantly influences mood and mental health. Consequently, changes in the gut microbiota population may occur when you kiss someone with an unhealthy oral microbiome, potentially introducing disruptive bacteria. Over time, this can lead to your gut signaling stress or sadness to your brain.
Sometimes, alterations in the oral microbiome can result from specific sexual behaviors during intimate contact. Any oral contact with the genitals, particularly female genitals, can affect the oral microbiota. This is because the female genital microbiome differs significantly from the mouth ecosystem and is often richer in Lactobacillus, whereas the mouth is typically dominated by Streptococcus and Veillonella. In a case report study examined how the microbial communities in the vagina, penis, and mouth change after sexual intercourse. It highlights that sexual activity can lead to significant shifts in the microbiota of these body sites, with bacteria being exchanged between partners. The findings suggest that sexual intercourse plays a role in altering microbial composition, which could have implications for understanding infections, microbiome health, and sexual health. Further research is needed to explore these changes in larger populations [4].
While mental health risks do not come from alterations in the microbiome alone, romantic relationships may pose physical health and psychological risks, such as anxiety and depression, through the transfer of microbes. This exchange can potentially shift your oral and systemic health toward microbiome imbalance and inflammation, particularly in situations of unprotected sexual relationships and poor hygiene. Although this is not a guaranteed outcome, it represents a subtle and insidious pathway that science is still exploring. Along with these hazardous risks, the transmission of the herpes virus, which is a significant risk factor for ovarian cancer, should also be noted in the context of relationships and intimate contacts.
