1 eISSN 1303-5150 www.neuroquantology.com NeuroQuantology | May 2019| Volume 17 | Issue 06 | Page 01-09| doi: 10.14704/nq.2019.17.06.2189 Homayouni-Rad A and Pourjafar H. Prebiotcs, as Promising Functonal Food to Patents with Psychological Disorders: A Review on Mood Disorders, Sleep, and Cogni ton Prebiotcs, as Promising Functonal Food to Pa ten ts with Psychological Disorders: A Review on Mood Disorders, Sleep, and Cogniton Aydin Tabrizi 1 , Leila Khalili 2 , Aziz Homayouni-Rad* 3 , Hadi Pourjafar* 4 , Parvin Dehghan 2 , Fereshteh Ansari 5,6,7 Key Words: prebiotics, psychological disorders, mood, depression, anxiety, tress, sleep, cognition DOI Number: 10.14704/nq.2019.17.06.2189 NeuroQuantology 2019; 17(06):01-09 *Corresponding author: Aziz Homayouni-Rad and Hadi Pourjafar Address: 1 Pediatric Neurology Research Center, Research Institute for Children’s Health, Shahid Beheshti University of Medical Sciences, Tehran, Iran; 2 Department of Nutrition, Faculty of Nutrition and Food Sciences, Tabriz University of Medical Sciences, Tabriz, Iran; 3 Department of Food Science and Technology, Faculty of Nutrition and Food Sciences, Tabriz University of Medical Sciences, Tabriz, Iran; 4 Department of Food Sciences and Nutrition, Maragheh University of Medical Sciences, Maragheh, Iran; 5 Research Center for Evidence-Based Medicine, Health Management and Safety Promotion Research Institute, Tabriz University of Medical Sciences, Tabriz, Iran; 6 Iranian EBM Centre: A Joanna Briggs Institute Affiliated Group; 7 Ph.D. of Epidemiology, Razi Vaccine and Serum Research Institute, Karaj, Iran. e-mail  Homayounia@tbzmed.ac.ir (Dr. Aziz Homayouni); pourjafarhadi59@ut.ac.ir (Hadi Pourjafar) Relevant conflicts of interest/financial disclosures: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. Received: 25 April 2019; Accepted: 21 June 2019 ABSTRACT Objective: Manipulating the intestinal microbiota for the benefit of the mental health is a concept that has become widely acknowledged. Prebiotics, the nondigestible nutrients, can proliferate intrinsic beneficial gut bacteria, and so provide an alternative strategy for effectively altering the enteric ecosystem, and then brain function. This review summarizes findings from studies using prebiotics to improve mental health and psychological disorders. Methods: Pub Med, Google Scholar, Scopus, and Science Direct databases were searched by using “prebiotics”, “psychological disorder”, “mood disorder”, “depression”, “anxiety”, “stress”, “sleep”, and “cognition” for the studies aiming the application of prebiotics and the beneficial effects of them in mental health and psychological disorders’ control and/or treatment. Results: Prebiotic consumption improved psychological and biological measures of mental disorders such as depression, anxiety, and stress in individuals with mood disorder. Overall, the results showed that, through modulating the gut microbiota composition, prebiotics can beneficially affect mental health, modulate psychological disorders, and improve cognitive function and sleep/wake cycle disruptions. Discussion: Prebiotics can improve mental health, mood, and psychological function. Habitual diets rich in dietary prebiotics would be linked to reduced risk of developing symptoms of psychological disorders; however, additional studies are necessary. Introduction A psychological disorder, also known as a mental disorder, is a pattern of behavioral or psychological symptoms characterized by a clinically significant disturbance in an individual’s cognitive, emotion regulation, or behavior that are usually associated with significant distress in social, occupational, or other important activities (Lai et al., 2018). Psychological disorders affect over one billion people all over the world. Common mental disorders refer to a range of anxiety and depressive disorders. Globally, it is estimated that 4.4% of the global population suffer from depressive disorder, and 3.6% from anxiety disorder (FAO/WHO, 2017). Traditionally