Stressors can produce profound health consequences. In one epidemiological study, for example, all-cause mortality increased in the month following a severe stressor – the death of a spouse. Theorists propose that stressful events trigger cognitive and affective responses which, in turn, induce sympathetic nervous system and endocrine changes. These ultimately impair immune function. Potential health consequences are broad, but include rates of infection, HIV progression, and cancer incidence and progression.