Stress over the Life Course and Mood Disorders

Abstract

Background: The role of stress across the life course and the stress sensitisation theory has been demonstrated in western settings. However, the applicability of stress sensitisation, whereby childhood adversity increases the vulnerability to depression following adult stressful life events, to other populations and other mood disorders is unclear. We therefore (1) examined the role of stress across the life course in the development of depression in a Chinese population, and (2) extended the stress sensitisation theory to bipolar disorder in a western population. Methods: (1) We investigated the association of childhood adversities and adulthood stressors with depressive symptoms and mild or moderate-to-severe depression in the crosssectional analyses of 9,729 Chinese participants from phase 3 of the Guangzhou Biobank Cohort Study (2006-2008). (2) We investigated the association of childhood adversities and adulthood stressors with initial-onset and recurrent DSM-IV manic episodes in 33,375 U.S. participants during the National Epidemiologic Survey on Alcohol and Related Conditions’ 3-year follow-up period (2001-2005). Results: (1) Depression was present in 14.5% of the sample. Childhood adversities were associated with mild depression (odds ratio [OR] 1.78, 95% confidence interval [CI] 1.58- 2.02) and moderate-to-severe depression (OR 2.30, 95% CI 1.68-3.15), adjusted for age, sex, education, and childhood socio-economic status. Past-year adulthood stressors were associated with mild depression (OR 1.96, 95% CI 1.54-2.02) and moderate-to-severe depression (OR 3.55, 95% CI 2.21-5.68), adjusting additionally for occupation and income. Adulthood stressors were more strongly associated with depressive symptoms among those with a history of childhood adversities. (2) A manic episode was experienced by 2.3% of participants during the follow-up period. Childhood physical abuse and sexual maltreatment were associated with both first-onset mania (OR for abuse 2.23, 95% CI 1.71-2.91; OR for maltreatment 2.10, 95% CI 1.55-2.83) and recurrent mania (OR for abuse 1.55, 95% CI 1.00-2.40; OR for maltreatment 1.60, 95% CI 1.00-2.55). Past-year adulthood stressors in the domains of interpersonal instability and financial hardship were associated with incident and recurrent mania. Exposure to childhood adversity potentiated the association of recent stressors with adult mania. Conclusions: Our findings demonstrate a role of life course stress in depression and the initial onset of bipolar disorder, as well as in the prospective course of bipolar. These are consistent with aetiologic models of mood disorders that implicate deficits in developmentally established stressresponse pathways. Clinical assessment of stress across the life course could provide better risk-stratification for mood disorders and facilitate earlier detection and better management, although this would require evidence from further studies. As childhood adversity occurs during a developmental period and is correlated with subsequent stressors in adulthood, thus interventions at both early and later stages of the life course may be required to reduce the impact of stress on mental health.