Application of Probiotics in the Treatment and Support of Mood Disorders

In today’s increasingly developed society, the growing pressures of life and life’s obstacles lead to changes in psychological and behavioral aspects, which can manifest as either positive or negative expressions. It is crucial to distinguish between changes in normal behavior due to stress-induced mood alterations and those indicating more serious issues. Behaviors become noteworthy when the issues are severe and prolonged, impacting an individual’s daily activities and being a significant global burden [1]. Mood disorders adversely affect the health burden [2].

Mood disorders, also known as emotional disorders, involve emotional states becoming excessively severe, where individuals find it difficult to control, leading to depressive moods and a decline in learning, work, and communication abilities with those around them [3, 4]. Mental health professionals can treat these emotional disorders. It is important to provide assistance to reduce unnecessary anxieties. Emotional disorders may recur and worsen over a person’s lifetime if not intervened in a timely manner.

Signs of Mood Disorders

Individuals with mood disorders almost always feel excessively sad or overly cheerful and typically exhibit the following symptoms:

• Always feeling anxious, hopeless, or having a “void” feeling; a mood of dejection, pessimism; feeling guilty, worthless, or helpless; inability to concentrate and make decisions; thoughts of death or suicide; suicide attempts.
• Restlessness, irritability, excessive or unusual disappointment, abnormal irritability; inappropriate communication behaviors.

How are Mood Disorders Treated?

Researchers have not yet fully understood the true causes of mood disorders. Generally, mood disorders arise from a combination of genetic factors, along with various other biological and social factors. The impact of emotions on cognition is extremely crucial. The brain influences cognition and experiences, affecting intellectual development. Some other reasons indicate the involvement of the gut microbiota in many issues related to the origin of nerve system-based disorders, affecting the relationship between the digestive microbiota and mood disorders [3]. To achieve effective treatment, proper diagnosis of these disorders is essential.

According to evaluations by mental health experts, most cases require clinical assessments by physicians to eliminate risk factors that contribute to these symptoms. Treatment measures usually involve psychological therapy and/or medication. Typically, the best treatment approach involves a combination of both. Moreover, a significant proportion of patients do not respond well to existing medications [5, 6]. Regarding psychological treatment, research indicates that specific psychotherapeutic or cognitive-behavioral therapies are particularly helpful for adolescents with depression.

The Role of the Gut Microbiota in Mood Disorders

Humans harbor various types of microorganisms in certain parts of the body, such as the eyes, mouth, rectum, and gastrointestinal (GI) tract [4, 7]. The gut microbiota is extremely diverse, with at least 1,000 different species and over 3 million genes. Thus, abnormal gut microbiota may play a role in the pathophysiology of some central nervous system (CNS) disorders  [8]. However, human studies have shown the complexity of interactions between the CNS and the gut microbiota. The bidirectional relationship between the gut microbiota and the brain has long been recognized and is considered to primarily occur within the autonomic nervous system, enteric nervous system, and the immune system [9]. In mouse studies, some research on the influence of the microbiota system on mouse cognition evaluated the formation of new memories in mice infected with the Gram-negative bacterium Citrobacter rodentium [10]. Animals infected with Citrobacter rodentium and raised in stressful environments exhibited impaired non-spatial cognitive states, even after eliminating the infection. The movement of symbiotic microbiota through the GI barrier is a recognized factor that promotes persistent immune inhibition and is considered one of the factors that leads to emotional disorders.

 

Naseribafrouei and colleagues (2014) conducted a study on the correlation between the gut microbiota composition in human feces and mood disorders [11]. They compared the composition of the gastrointestinal microbiota between depressed individuals and the control group, finding that the Alistipes and Oscillibacter strains were overexpressed in some individuals with mood disorders. Alistipes is associated with both chronic fatigue syndrome and irritable bowel syndrome (IBS). In older patients, an imbalance in the gut microbiota related to digestion is associated with other health issues, and researchers have also noted the link between depressive symptoms and gut microbiota disorders [12]. Disorders of the gut microbiota are at risk of developing high mental symptoms  [13]. Individuals with IBS have been observed to have a high prevalence of mental illnesses, mainly anxiety and depression disorders. Another retrospective cohort study conducted from 2000 to 2005 evaluated the association between IBS and depressive disorders. The IBS sample included about 4,000 patients, and the control group comprised approximately 18,000 randomly selected individuals without IBS. The risk of depressive disorders, anxiety disorders, and sleep disorders in the IBS group was significantly higher than in the control group  [14].

Potential of Probiotics in Treating Mood Disorders

The concept of psychobiotics, which are bacterial-based treatment methods with overall health benefits, is rapidly gaining attention. Given the possible systemic effects, the gut microbiota is currently attracting interest in the field of neuroscience. The utilization of bacteria already present in the intestinal system makes probiotics also considered useful by researchers. The mechanisms of action of probiotics are determined in one of three ways: (i) controlling the concentration of gut microbiota, (ii) protecting the integrity of the intestinal lining, or (iii) preventing changes and variations in bacteria responding to the immune system locally related to the gut [15].

Several clinical studies have suggested that probiotic therapy may help treat various diseases and may slow the development of certain conditions, such as allergies in children, diarrhea, bacterial vaginosis, and IBS [16-18]. Researchers believe that probiotic therapy may be helpful for all patients undergoing treatment for mood disorders, although they may experience short-term side effects, typically involving mild gas and bloating. Some effects of biological products may represent an opportunity to treat mood disorders.

The researchers implemented daily supplementation with Lactobacillus helveticus in mice during stress until the end of the study and utilized the selective serotonin reuptake inhibitor citalopram as a positive control. In this study, L. helveticus improved stress-induced behaviors (anxiety and depression) and psychiatric disorders, essential for treating emotional disorders. In a clinical study, the research group evaluated the impact of probiotic treatment (Bifidobacterium bifidum, Bifidobacterium lactis, Lactobacillus acidophilus, Lactobacillus brevis, Lactobacillus casei, Lactobacillus salicylicrius, Lactococcus lactis) on improving mood and reducing depressive symptoms in perimenopausal women (ClinicalTrials.gov: NCT04753944), with initial results showing promising outcomes in treating mood disorders.

In summary, the gut microbiota can act as a dynamic entity, influencing and being influenced by various genetic factors related to both bacteria and hosts, age, diet, weather, sensitivity to antigens, and exposure to antibiotics. Currently, mental health professionals are exploring patients’ diets and are open to applying new methods, such as psychobiotics, in treating mood disorders.

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