The aim of the study is to evaluate the clinical efficacy of a known diuretic drug, Bumetanide, in terms of improvement of memory and psychological functioning in children and adolescents with Down syndrome (DS), in order to develop therapeutic strategies for cognitive and psychopathology aspects associated with the syndrome. The study also aims to identify possible predictors and biological and genetic markers related to the efficacy of the treatment. Recently, preliminary studies conducted on the animal model of Down syndrome have proven the efficacy of the drug Bumetanide in counteracting some brain anomalies related to communication between nerve cells (synaptic transmission) typical of the syndrome, with the effect of improving memory skills. Behaviour-enhancing effects have also been found in preliminary studies in humans with other neurodevelopmental disorders (e.g., autism spectrum disorders). The drug Bumetanide could therefore be useful in counteracting the biological mechanisms that cause some cognitive deficits associated with Down syndrome. The potential of this therapeutic approach will be tested through a clinical trial in a population of children and adolescent patients with DS, in a randomized placebo-controlled trial with a three-month treatment with Bumetanide. Participants will be randomly assigned to the experimental group that will receive the treatment (Bumetanide) vs the control/comparison group that will receive the placebo. Bumetanide is a diuretic drug that has been widely used in humans in the past with few side effects, is orally active, and is very inexpensive. 64 participants will be recruited.