Depression is the leading cause of disability worldwide. Neuroscientists from Synapsy—the Swiss National Centre of Competence in Research into Mental Illness—based at Lausanne University Hospital (CHUV) and Lausanne University (UNIL) have recently demonstrated that lactate, a molecule produced by the body during exercise, has an antidepressant effect in mice. Lactate is best known for the pivotal role it plays in the nutrition of neurons inside the brain. Yet it can also counter the inhibition of the survival and proliferation of new neurons, a loss seen in patients suffering from depression and in stressed animal. Furthermore, the research team pinpointed NADH as a vital component in the mechanism: this is a molecule with antioxidant properties that is derived from the metabolism of lactate. The findings, published in the scientific journal Molecular Psychiatry, provide a better understanding of the physiological mechanisms that underpin physical activity, which should lead to an improvement in the way depression is treated in the future.