Psychological diseases are not just in your head. Recent studies have shown that various disorders such as autism spectrum disorder, anxiety, depression, and schizophrenia are sensitive to changes in the gut microbiome and the use of antibiotics and pro- or prebiotics. Autism spectrum disorder (autism) is associated with elevated Bacteroidetes Proteobacteria, but lower numbers of Bifidobacteria and Firmicutes when compared to healthy children. Further, it is associated with a lower number of Prevotella species, despite the overall abundance of Bacteroidetes in children with autism. And bacteria from the genus Sutterella and Ruminococcus children are elevated in children with autism. Additional but widely varying associations have been suggested between the gut microbiota and anxiety, depression, and even the risk of developing schizophrenia. This gut-brain connection puts everyone affected on a quest for a possible probiotic treatment. Frustratingly, current research results are not sufficient to draw reliable conclusions about the clinical potential of microbiota-based therapy strategies when it comes to neuropsychological disorders.