The present invention relates to a device, system and method for determining an emotional state of a user based on emotion-induced cortisol estimation. The device comprises an interface (11) for obtaining a psychophysiological signal trace (22) indicative of one or more measured stimulus responses corresponding to a neural stress response； a processing unit (12) for processing the psychophysiological signal trace, wherein the processing unit is configured to determine one or more stimulus responses (29) in the psychophysiological signal trace (22)； to determine a first contribution (91) to an estimated future cortisol level trace (93) based on the one or more determined stimulus responses (29) in the psychophysiological signal trace (22)；to determine a second contribution (92) to the estimated future cortisol level trace (93) based on one or more anticipated future stimulus responses (96)； and to determine an estimated future emotional state of the user based on said first and said second contribution to the estimated future cortisol level trace (93). The invention further relates to a corresponding computer program and a wearable device (30).
