In the population-based Malmö Diet and Cancer Study Cardiovascular Cohort (MDC-CC), we recently found that high copeptin, indicating overactivity of the AVP system, was independently associated with obesity, insulin resistance and the risk of development of DM (12, 13, 14), and similar results have also been observed in a Dutch and a US population (15, 16); however, whether these associations are causal or not is unknown. This evidence concerns the gene AVP and diabetes mellitus.