Imagine tracking your feelings during daily interactions with your romantic partner. What would you learn? That's what approximately 100 heterosexual couples in Montreal did each day for 3 weeks during a study run by researchers from McGill University. They were interested in whether a fairly common genetic variant in the opioid system, seen in about a quarter of the population, was associated with feelings of insecurity in romantic relationships. Their results, published in the journal Molecular Psychiatry, suggest that, in some cases, there may indeed be a link.