Objective: To investigate the emotional reactivity to small disturbances in daily life in patients with non-affective psychosis (NAP), bipolar disorder (BD) and major depression [major depressive disorder (MDD)]. Method: Forty-two patients with NAP, 38 with BD, 46 with MDD, and 49 healthy controls were studied with the experience sampling method to assess (i) appraised subjective stress of small disturbances in daily life and (ii) emotional reactivity, reflected in changes in positive affect (PA) and negative affect (NA). Results: Multilevel regression analyses showed an increase in NA in MDD, a decrease in PA in BD and both an increase in NA and a decrease in PA in NAP in association with the subjectively stressful situations, compared with the control subjects. Conclusion: Individuals with NAP, MDD and BD display differences in emotional stress reactivity. Type of mood disorder may exert a pathoplastic effect on emotional reactivity in individuals with MDD and BD. Individuals with NAP may be most vulnerable to the effects of daily life stress.