Review Article

Psychobiotics, Novel Therapeutic Agents for the Psychiatric Disorders

Praveen Reddy P., K. Sandhyaand Aparna Srikantam*

Department of Microbiology, School of Allied and Healthcare Sciences, Malla Reddy University, Maisammaguda, Dulapally, Hyderabad-500100, Telangana, India.

Received | December 25, 2024; Revised | January 11, 2025; Accepted | January 21, 2025; Published | February 04, 2025

*Correspondence | Aparna Srikantam, Department of Microbiology, School of Allied and Healthcare Sciences, Malla Reddy University, Maisammaguda, Dulapally, Hyderabad-500100, Telangana, India; Email: [email protected]

Citation | Praveen, R.P., K. Sandhya and A. Srikantam. 2025. Psychobiotics, novel therapeutic agents for the psychiatric disorders. Novel Research in Microbiology Journal, 9(1): 28-40.

DOI | https://dx.doi.org/10.17582/journal.NRMJ/2025/9.1.28.40

Keywords | Neurological disorders, Psychobiotics, Probiotics/prebiotics, Gut-brain axis, Clinical trials

Copyright: 2025 by the authors. Licensee ResearchersLinks Ltd, England, UK.

This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).

Introduction

Currently, mental disorders, including Parkinsons’s disease, anorexia nervosa, Alzheimer’s disease, autism in children, clinical depression, anxiety, stress, insomnia, and schizophrenia are prevalent worldwide (Oroojzadeh et al., 2022). Especially, clinical depression is the most common global psychological issue. Around 3.8% of people worldwide are suffering from depression that is affecting their abilities and quality of life. The depression is a severe sociomedical issue and individuals suffering from it are at a high suicidal risk. The patients suffering from clinical depression are being treated by conventional antidepressant therapy; however, only around 70 % of the patients are responding to this conventional antidepressant treatment. Hence, for treatment of the remaining 30 % patients (who are not responding to the antidepressant therapy), it is mandatory to identify/ discover alternative and safe methods of therapy (Dziedzic et al., 2024). Similarly, several other psychiatric disorders are also not cured effectively by the current traditional drugs and even some patients are completely resistant to the traditional therapeutic agents. Current research studies and various clinical trials revealed that psychobiotics (probiotics or prebiotics or both) when administered orally, serve as an alternative and effective agents for the treatment of the various psychiatric disorders. The objectives of this study are to make an emphasis on the concept of psychobiotics, their modes of action, and significant therapeutic uses of psychobitocs (i.e., probiotics and prebiotics) in counteracting the manifestations of the mental disorders.

Microbiota-gut-brain axis

The two-way communication between the central nervous system and the gut microbiota constitutes the Microbiota-gut-brain axis. The gut microbiota includes the various microorganisms residing in the gut and their genomes. The microbiota-gut-brain axis is a network through which both gut microbiome and brain jointly regulate the health. The microbiota-gut-brain axis is a system consisting of enteric nervous system, central nervous system, and endocrine system, including immunological, neuro-related, and metabolic regulatory compounds. Though the brain and gut are located at different regions in the human body, there are several theories that proposed various pathways by which the gut microorganisms coordinate with the central nervous system. The gut microorganisms produce or induce the secretion of certain neurotransmitters such as serotonin, gamma-aminobutyric acid, and dopamine (Magalhaes-Guedes, 2022).

The enteric nervous system is equipped with millions of nerve cells, which are located in the mucosa of gut, and regulate the various functions of the gut region. The direct interaction between intestinal tract and central nervous system occurs through a vagus nerve (De Lartigue et al., 2011). The vague nerve originates from the brain stem, and stimulates the gut region and enteric nervous system. The entire gut region is stimulated by a vague nerve that includes 80 % afferent and 20 % efferent fibers. The afferent fiber terminals of a vague nerve respond to the inflammatory chemicals, dietary ingredients, metabolic products released by bacteria (beneficial/ probiotic) and gastrointestinal regulatory peptides, and transfer signals to the brain. (Waise et al., 2018).

The non-clinical studies conducted on human beings revealed that gut microorganisms regulate public behavior, anxious behavior, and bodily performance (Oroojzadeh et al., 2022). The human gut microflora plays a key role in maintenance of health. The decreased Lactobacillus and Bifidobacterium population in the gut region results in major depressive disorder (depression). In the gut region of patients suffering from Alzheimer’s disease, the Bifidobacterium species number is very low. In autism patients, a lower bacterial biodiversity has been reported. Disturbance in the gut microflora may lead to the occurrence of attention deficit hyperactivity disorder (Cheng et al., 2019).

Probiotics, prebiotics and psychobiotics

Probiotics: Probiotics are defined as microorganisms that when consumed in enough quantities improve health conditions of the host (Reid et al., 2019). The term, probiotics was first used by Lilly and Stilwell (1965), which means “for life” in Greek. Probiotics are regarded as functional foods, resembling traditional foods, but exhibit physiological functions, increase nutritional quality, and regulate gut health (Ailioaie and Litscher, 2021).

Prebiotics: The prebiotic is an ingredient associated with our dietary components that is not utilized (digested) by the human body, and is resistant to the action of gastric and enteric enzymes. Prebiotics are selectively used by certain gut bacteria that ferment them to produce various metabolites, which in turn improve the human health. Thus, prebiotics enhance growth of the beneficial bacteria that maintain the overall health of the host (You et al., 2022).

Psychobiotics: The concept of psychobiotics was first used in 2012, and were described as microorganisms that when consumed in enough quantity, confer relief to the individuals suffering from the psychological disorders. The psychobiotics include probiotics and prebiotics that can enhance the mirobiota-gut-brain axis signals and improve neurological related actions such as behavior, thinking and reasoning, and nervousness (Evernel et al., 2019). In the gut, psychobiotics express antidepressant and anxiolytic effects through the gut-brain axis. Thus, they exert positive influence on the cognitive health and the emotional behavior (Oroojzadeh et al. 2022). Furthermore, psychobiotics can be defined as beneficial bacteria (probiotics) or ingredients (prebiotics) that support such beneficial bacteria, which enhance the gut bacteria and brain coordination (Sarkar et al., 2016). Moreover, the psychobiotics can be considered as future probiotics for the central nervous system, and could be regarded also as unique class of probiotics that exert positive influence on functions of the nervous system and may be employed for treatment of the various psychological disorders (Kwak et al., 2023).

Mechanisms of action of psychobiotics

The mechanisms of action of psychobiotics basically involve three modes, mainly (i) influencing the hypothalamic-pituitary-adrenal axis stress response and lowering systemic inflammation, (ii) exerting direct influence on the immune system, and (iii) releasing of neurologically active molecules such as proteins, short chain fatty acids, and neurotransmitters (Table 1 and Figure 1) (Kimse et al., 2024).

Psychobiotics in the gut region produce extracellular vesicles that contain the cellular components of the bacteria. The blood absorbs these extracellular vesicles from the gut and through blood circulation, they reach the brain. Thus, the extracellular vesicles release various neurologically active molecules and influence the functions of the central nervous system (Bleibel et al., 2023).

Potential psychobiotic microbial strains

Some of the potent bacterial strains that can be developed and used as psychobiotics include:

Lactobacillus helveticus: Lactobacillus helveticus is a Gram-positive bacillus that produces lactic acid. It is usually used as starter culture during milk fermentation for the production of cheese. It possesses usual probiotic features such as surviving in gut, attaching to epithelial cells, and controlling intestinal pathogens. Above all, it can be employed for the treatment of stress induced visceral complications (Ait-Belgnaoui et al., 2018).

Escherichia coli: The Escherichia coli is a Gram-negative, rod-shaped bacterium living in the gut region. Till date, extensive researches have been conducted on the probiotic characteristics of E. coli. Several experimental studies revealed that E. coli can be used for treatment of several psychological issues, especially stress (Beimfohr, 2016).

 

Table 1: List of neurologically active substances produced by psychobiotics in the gut region.

Psychobiotics in the gut region	Neurological metabolites released	References
Lactobacillus plantarum	Acetyl choline	(Chen et al., 2021)
Enterococcus faecium BS5	Gamma amino butyric acid	(Bs et al., 2021)
Bifidobacterium infantis	Tryptophan and serotonin precursor	(Desbonnet et al., 2008)
Escherichia coli	Norepinephrine, serotnin, and dopamine	(Chen et al., 2021)
Bacillus amyloliquifaciens SB-9	5-hydroxy tryptophan, Melatonin, and serotonin	(Jiao et al., 2016)

 

Bifidobacterium longum: Bifidobacterium longum is a Gram-positive, rod shaped bacterium occurring in the intestine of humans. The Bifidobacterium species are known for their potent probiotic effects. Bifidobacterium species are used for treatment of stress induced visceral problems via modulating the nervous functions and optimizing the hypothalamic-pituitary-adrenal axis activities. The human clinical studies revealed that Bifidobacterium species, solely or combined with other probiotic bacterial strains, have cured and/ or prevented various complications (Ait-Belgnaoui et al., 2018).

Bifidobacterium infantis: Bifidobacterium infantis is a symbiotic bacterium existing in the human gut. It has a unique ability of selectively utilizing the oligosaccharides present in the human milk. Hence, researchers assumed that B. infantis can be specifically used for health benefits of premature infants (Batta et al., 2023).

Clostridium butyricum: The Clostridium butyricum is a Gram-positive, rod shaped, strictly anaerobic, and endospore forming bacterium. It produces butyric acid and lives in the gut region of humans and animals. C. butyricum is a bacterium with potent probiotic properties, which can be used for treatment of gastrointestinal infections. It exerts positive effects by secreting several metabolites such as short chain fatty acids, propionic acid, acetic and butyric acids (Seki et al., 2003).

Lactobacillus rhamnosus: Lactobacillus rhamnosus is a Gram-positive, rod shaped, and facultative anaerobe. It is heterofermentative lactic acid bacterium. Several studies proved L. rhamnosus as a potent probiotic bacterial species due to its unique growth features, mainly resistance to acids and bile juice, and adequate adhering ability to the epithelial layer of the intestine. It is the most widely employed probiotic bacterial species, and is currently available in the markets as a commercial probiotic product (Segers and Lebeer, 2014).

Lactobacillus plantarum: The L. plantarum is a Gram-positive, rod shaped, and aerotolerant bacterium. It widely exists in meat and meat products, milk and milk products, and fermented products. It lives in the gastro-intestinal tract of human beings and confers several health benefits (De Vries et al., 2006). The following Table 2 presents some of bacterial species that experimentally act as effective psychobiotics.

 

Table 2: Psychobiotic bacterial strains used in clinical trials and proved to be effective in the treatment of psychiatric disorders (Cichonska et al., 2023).

Psychobiotic bacterial Strains	Clinical trial/experiment model	Beneficial effects observed
Lactiplantibacillus plantarum C29	Human volunteers with slight cognitive disorder	Improvement of cognitive behavior
Lactiplantibacillus plantarum DR7	Humans suffering from stress	Improvement of cognitive functions and memory and increased serotonin production
Lactibplantibacillus plantarum P8	Stressed humans	Reduction of anxiety symptoms and improvement of memory and cognitive behavior
Lactobacillus helveticus NS8	Rats with chronic stress	Reduced symptoms of anxiety and depression and improvement of cognitive functions
Lacticaseibacillus rhamnosus JB-1	Mice	Reduction of corticosterone associated with stress and improvement of anxiety and symptoms
Lacticaseibacillus rhamnosus GG	Older and middle aged adult volunteers	Improvement of cognitive abilities
Lactobacillus gasseri CP2305	Younger adults induced with chronic stress	Reduction of anxiety and sleeplessness.
Bifidobacterium breve A1	Patients suffering from Schizophrenia	Improvement of anxiety and depression symptoms
Bifidobacterium bifidum ATCCVR 29521	Wistar rats	Reduction of dead cell number and enhanced release of acetylcholine in the brain of rats suffering from Alzheimer’s disease
Bacillus coagulans MTCC 5856	Patients suffering from major depressive disorder and intestinal bowel syndrome	Reduced symptoms of depression and intestinal bowel syndrome

 

Therapeutic applications of psychobiotics

Alzheimer’s disease: The Alzheimer’s disease (AD) is linked to various factors like increase of age, genetics, head damage, vascular complications, microbial infections, and environmental pollutants. Up to date, the exact causes for the Alzheimer’s disease are not known. Various theories have been proposed for the cause of Alzheimer’s disease, out of which two have been considered. The first one is abnormality in cholinergic activity, while the other is variation in amyloid beta protein secretion. However, no hypothesis is accepted for the cause of Alzheimer’s disease (Breijyeh and Karamn, 2020). In the Alzheimer’s patients, accumulation of neurofibrillary tangles and amyloid plaques is observed with interrupted functioning of cholinergic nerves in the base portion of forebrain. These patients suffer from memory issues and cognitive disorders (Kumar et al., 2015). The treatment of Alzheimer’s disease aims to enhance the acetylcholine concentration and control the degeneration of cholinergic nerve cells in the brain region. Research studies reported that the malfunctioning of mitochondrion with increased age, leads to a low cellular energy production and increase of reactive oxygen species (ROS). High concentrations of ROS may cause damage to the cellular macromolecules, which can be linked to the Alzheimer’s disease (Mufson et al., 2008).

A previous studys conducted on amyloid beta induced AD mice model by Kobayashi et al. (2017) revealed that the cognitive abnormalities can be treated by employing a probiotic bacterial strain, named B. breve strain A1. Upon administration of B. breve strain A1into AD mice, there was a decreased state of the altered behavior in the treated mice. The mode of action of this probiotic strain was assumed to be control of the amyloid beta induced immune response and neuroinflammation (Kobayashi et al., 2017). The mixture of probiotic lactic acid bacteria and Bifidobacteria prevented the damage of brain and amyloid beta aggregations in AD mice during the initial stages of the disease (Bonfili et al., 2017). When a mixture of probiotic B. longum, L. acidophilu, B. lactis, and L. ferment was administered into the mice injected with amyloid beta1-42 (intra hippocampal), an improvement of the clinical features was observed, including place memory, stress due to oxidation, and learning deficiencies. Various previous studies conducted by Zhang et al. (2017), Nagpal et al. (2019), Yue et al. (2021) on animal models reported that probiotics can be used for the treatment/prevention of Alzheimer’s disease. Although studies on human beings are ongoing, but still much evidence is required to prove the role of probiotics in combating the Alzheimer’s disease.

Parkinson’s disease

The Parkinson’s disease is a neurological (neurodegenerative) complication occurs when the brain is devoid of dopamine. Dopamine acts as a neurotransmitter and regulates various functions such as memory, cognitive abilities, movement, sleep, and other functions. The dopamine deficiency in the brain of Parkinson’s disease patients is responsible for motor deficiency and may be the cause of cognitive disabilities (Emamzadeh and Surguchov, 2018). Zhu et al. (2012) reported that during the catecholamine synthesis in the brain, the enzyme, tyrosine hydroxylase catalyzes the rate-limiting reaction step in catecholamine biosynthetic pathway. Decreased synthesis of tyrosine hydroxylase results in the low production of dopamine and thus leads to Parkinson’s disease.

Based on their in vitro and in vivo experiments on Parkinson’s disease patients, Castelli et al. (2020) reported that upon consumption of SLAB51 (i.e., a nine probiotic living bacteria formulation, which contains Streptococcus thermophilus, B. longum, B. breve, B. infantis, L. acidophilus, L. plantarum, L. paracasei, L. delbrueckii subsp. bulgaricus and L. brevis) an enhanced tyrosine hydroxylase immune reactivity and protected dopaminergic neurons in the brain region (mainly, striatum and substantia nigra) was observed. Clinical studies conducted by Tamtaji et al. (2019) reported that administration of a probiotic mixture of L. reuteri, L. acidophilus, B. bifidum, and L. fermentum into patients suffering from Parkinson’s disease resulted in an improvement of the patient’s condition. Numerous probiotic bacteria release tyrosine decarboxylase in the gastrointestinal tract that synthesizes dopamine from levodopa. In the intestine of Parkinson’s disease patients, the concentration of levodopa becomes decreased when the patients are administered with probiotics (Van Kessel et al., 2019). Perez et al., (2015) reported that tyrosine decarboxylase gene was identified in many bacterial strains, more particularly in the species of Enterococcus and Lactobacillus.

Depression

The major depressive disorder (MDD) is a serious mental disorder, its symptoms include sleeplessness, anhedonia, fatigue, suicidal tendency, guilty feeling, loss of appetite, and depressed mood (Ferrari et al., 2013). Depression ranks fourth among the global human health disorders. According to the World Health Organization (WHO), globally around 35,00,000 people are affected by depression and more than 8,00,000 are committing suicide annually. It is estimated that by 2030, the depression stands as first human health issue in the world. The pandemic situation due to COVID-19 has greatly increased the number of depression cases, where 27.6 % more cases have been reported compared to pre-pandemic conditions (Salari et al., 2020). Various antidepressant drugs are used to cure depression, including mirtazapine, monoamine oxidase inhibitors, selective serotonin reuptake inhibitors, non-selective serotonin and norepinephrine reuptake inhibitors, selective norepinephrine reuptake inhibitors, and other agents (Cryan and Dinan, 2015). The current drugs are ineffective on about 30 % of the MDD patients. Thus, new antidepressants and novel approaches are urgently needed (Miyanishi and Nitta, 2021). The recent studies reported by Bibbo et al. (2022); Radjabzadeh et al. (2022); Kumar et al. (2023) on the use of microbiota have presented a key connection between depression and gut microflora. Miyoka et al. (2018) reported that combination of traditional antidepressant drugs and probiotics proved to be effective for the treatment of patients who were resistant to conventional drugs. Various preclinical studies and clinical trials revealed that altering the gut microflora by administration of probiotic bacteria has proved to be effective in the treatment of depression and other health issues of humans (Gao et al., 2023).

The psychobiotics enhance absorption of nutrients, production of short chain fatty acids and gamma-aminobutyric acid (GABA), anti-oxidant properties, and counteract the cognitive disorders (Nosrani et al., 2021). All these activities/ products are associated, either directly or indirectly, with the control/ treatment of depression. Various probiotic bacterial strains (single strain/ mixture/ formulations) and fermented foods (i.e., rich with probiotics) have been tested for their effectiveness on treatment of depression (i.e., anti-depressive properties). In many previous studies, Bifidobacterium and Lactobacillus strains have been widely used (Gao et al., 2023; Merkouris et al., 2024; Rahmannia et al., 2024). In a recent study, a Gram negative bacterium; Akkermansia mucinipila, has displayed psychobiotic properties when used on a rodent model (Ding et al., 2021).

Anxiety disorders

The disorders associated with anxiety are quite common among humans (Thibaut, 2017). The most widely observed anxiety disorder is specific phobia, where the rate of prevalence is 12.1 % in a year, while the agoraphobia is the anxiety disorder with the least prevalence rate of 2.5 in a year. The females are more susceptible to anxiety compared to males; the anxiety ratio in males and females is approximately 1:2 (Remes et al., 2018). In the central nervous system, the key compounds that mediate the anxiety are assumed to be serotonin, gamma-aminobutyric acid (GABA), dopamine, and norepinephrine. A previous study revealed that autonomic nervous system; specifically sympathetic nervous system, is associated with the major anxiety symptoms (Martin et al., 2009).

In a previous study, Steenbergen et al. (2015) applied L. lactis W19, L. brevis W63, B. bifidum W23, L. casei W56, B. lactis W52, L. salivarius W24, and L. lactis W58 on twenty volunteers suffering from anxiety disorders for a period of four weeks. Interestingly, the obtained results showed that the participants displayed reduced sad mood associated with negative thoughts. It was assumed that the bacteria might have shown impact on serotonin. Luang-In et al. (2020) administered 6 probiotic bacterial strains (i.e. B. adolescentis TBRC 7154, Pediococcus pentosaceus WS11, L. lactis subsp. lactis TBRC 375, B. adolescentis TBRC 7154, L. plantarum SK321, and L. fermentum SK324); isolated from Thai fermented foods, on male Wistar mice for two weeks to study the effect of probiotic bacteria on the behavior of these mice. The trials results revealed that the treated mice had shown significantly decreased symptoms of anxiety. Moreover, Lee et al. (2021) tested the psychobiotic effect of B. adolescentis NK98 and L. reuteri NK33 (i.e., probiotic NVP-1704) on reducing the sleeplessness, stress, anxiety, and depression in healthy adults exhibiting sub-clinical symptoms. Results revealed that the probiotic NVP-1704 was effective in treatment of psychiatric disorders and insomnia.

Autism disorders

The autism spectrum disorders are serious neurological complications which occur in neonates and young children (Li and Zhou, 2016), and are manifested by abnormal social behavior. A previous report issued by the Global Burden of Diseases, Injuries, and Risk Factors (2016) revealed that 62.2 million children worldwide were affected by autism spectrum disorders. Various health issues such as depression, epilepsy, Tourette syndrome and anxiety, and gut related issues are also associated with autism spectrum disorders (Feng et al., 2023). Furthermore, the prevalence of these disorders may increase in due course, thus further studies on treatment of autism are required (Vos et al., 2023). Various factors are responsible for autism spectrum disorders including genetic and environment-related factors. Several recent studies provided enough evidence that the gut microorganism’s imbalance may induce the development of autism spectrum disorder symptoms, proving that gut bran-axis link is invalid (Ahmed et al., 2020). In the gut region of children suffering from autism spectrum with constipation, several deleterious pathogenic bacteria such as E. coli, Shigella spp., and Clostridium spp. have been detected in relatively high numbers (Straiti et al., 2017). In a recent study, the toxin producing C. histolyticum has been isolated from the fecal matter of autism children (Feng et al., 2023). In the urine of autism children, high levels of p-cresol and p-cresyl sulphate have been reported, where Clostridium spp. and Pseudomonas stutzeri are assumed to be the cause (Altieri et al., 2011).

Various clinical studies reported that psychobiotics (i.e., probiotics and prebiotics) can reduce the clinical features of autism and maintain the gut microbe balance (Shaaban et al., 2018; Meguid et al., 2022). Experiments on mice revealed that there is a considerable improvement in the emotional and social behavior in those mice upon administration of probiotics (Sunand et al., 2020). The prebiotic compounds occurring in wheat fiber control the harmful bacteria (i.e., Clostridium spp.) and enhance the growth of beneficial bacteria (i.e. Bifidobacterium spp.) (Lefranc-Millot et al., 2012). Muhammad et al. (2022) reported that probiotics (i.e., beneficial bacteria) in the gut region produce neurologically active compounds. L. brevis and B. denticola synthesize gamma-aminobutyric acid, while E. coli and Staphylococcus aureus produce dopamine. Recently, many researchers/clinicians use De Simone Formulation (DSF) supplement made up of 8 probiotic bacterial strains, mainly B. longum, L. paracasei, L. acidophilus, B. breve, L. delbrueckii subsp. bulgaricus, L. plantarum, B. infantis, and Streptococcus thermophiles for clinical treatment of autism children. This DSF formulation must be administered orally to the autism children for a period of six months (Santocchi et al., 2020).

Psychobiotic rich foods

Several previous studies conducted by Porras-Garcia et al. (2023); Shah et al. (2023); Balasubramanian et al. (2024) on human beings revealed that the intake of natural fermented foods, foods fermented by starter cultures/ individual microorganisms, and certain plant products reduced the manifestations of psychiatric disorders and cognitive issues. Kim and Shin (2019) study reported that in women, there were no noticeable effects of probiotic-rich food on the depression symptoms. On the other hand, in men, the clinical symptoms of depression have been reduced by the probiotic-diet. Oshawa et al. (2017) conducted a controlled, randomized, and double blind study on the middle aged adult healthy volunteers, who consumed 190 grams of milk fermented by L. helveticus every day for a period of eight weeks. In these volunteers, there were improvements in the cognitive behavior and memory. Many other studies also revealed that consumption of foods rich with psychobiotics (i.e., probiotics/prebiotics) has improved the complications associated with the neurological disorders (Karbownik et al., 2022; Dahiya and Nigam, 2022; Freijy et al., 2023). Table 3 demonstrates some of the foods rich with psychobiotics.

 

Table 3: Foods containing psychobiotics (Cichonska et al., 2023).

Psychobiotic food	Psychobiotic microbial strain(s) associated
Cheese and yoghurt	L. plantarum 299v
Ice cream	L. plantarum ATCC 8014
Skimmed milk with milk protein concentrate	Bacillus coagulans MTCC5856
Milk based dessert sauce	L. casei Shirota
Apple and watermelon juice	L. plantarum ATCC 8014
Whole soy beans	L. plantarum P8
Coconut milk and tomato juice	L. reuteri DSM 17938

 

Conclusions and Recommendations

The psychobiotics include both probiotics and prebiotics which when administered orally improve the microbiota-gut-brain axis interaction and counteract the neurological disorders. Various clinical trials and research studies have confirmed that the administration of psychobiotics (i.e., prebiotics and probiotics) can effectively prevent or treat the psychological disorders. Further, the foods, especially the fermented foods/ dairy foods containing probiotics/prebiotics, can improve the mental health when consumed regularly. In many studies, it has been revealed that patients who consume foods rich in psychobiotics exhibit reduced symptoms of psychiatric disorders compared to those who consume food devoid of psychobiotics. The administration of psychobiotics as therapeutic agents is still under study. Currently, researchers are using psychobiotics in combination with traditional drugs to treat those patients suffering from various psychiatric disorders. To improve the reliability of the current findings, it is recommended that future research studies must consider more rigorous and high standard approaches such as enhanced randomization and blinding methods. Furthermore, it is proposed these future researches should investigate the variety of treatment strategies to comprehend how the different psychobiotic strains and their combinations can enhance the therapeutic outcomes for the different ailments. In the future, psychobiotic formulations may become the sole potent drugs for treating the various neurological disorders.

Acknowledgements

The authors acknowledge the Management and Vice-Chancellor of Malla Reddy University for their support. The first and second authors express their thanks to the Dean, School of Allied and Healthcare Sciences, Malla Reddy University for her continuous encouragement and support in completing this review.

Novelty Statement

The current review provides a comprehensive analysis of the emerging field of psychobiotics, highlighting their potential as novel therapeutic agents for psychiatric disorders by modulating the gut-brain axis. Additionally, the review consolidates the latest research and clinical trials on psychobiotics, offering insights into their efficacy in treating various psychiatric conditions, including depression, anxiety and related complications.

Author’s Contribution

Praveen Reddy P: Conceptualization and formal analysis.

Praveen Reddy P, K. Sandhya and Aparna Srikantam: Investigation.

Praveen Reddy P. and K. Sandhya: Data curation and writing original drafts.

Praveen Reddy P and Aparna Srikantam: Reviewing, editing the manuscript and scientific corrections.

Conflict of interests

The authors have declared no conflict of interests.

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