Oxytocin, the feel-good bonding hormone released by physical contact with another person, orgasm and childbirth (potentially encouraging monogamy), might have a darker side. The love drug also plays an important role in intensifying negative emotional memories and increasing feelings of fear in future stressful situations, according to a new study.

Two experiments performed with mice found that the hormone activates a signaling molecule called extracellular-signal-related kinases (ERK), which has been associated with the way the brain forms memories of fear. According to Jelena Radulovic, senior author on the study and a professor at Northwestern University’s medical school, ERK stimulates fear pathways in the brain’s lateral septum, the region with the highest levels of oxytocin.