Maladaptive or uncontrolled impulsivity and compulsivity lead to emotional and social maladjustment, e.g. addiction and crime, and underlie psychiatric disorders. Recently, alterations in microbiota composition have shown to have implications for brain and social behaviors as we have been explaining in our lasts blogs. The microbiota-gut-brain axis may be involved in this process but the mechanisms are not fully identified (1). The supplementation of probiotics can modulate the microbial community and now has been suspected to contribute to ameliorating symptoms of a psychiatric disease with possible influence on social behaviors (2). To date, no randomized controlled trial has been performed