Population determinants of mood disorders

Abstract

A systematic understanding of prevailing and emerging population determinants is critical to the prevention of mood disorders. Yet it is unclear whether stress sensitisation, based on the diathesis-stress model, is contextually specific and relevant to other mood disorders. Social movements are increasing globally and could represent an emerging determinant of mood disorders. We therefore applied epidemiological approaches to population-based cohorts (n=90,383) in contrasting settings: a rapidly emerged Chinese city (Guangzhou), a neighbouring developed Chinese city (Hong Kong) and a Western developed country (US):- (1) to extend the stress sensitisation hypothesis to a spectrum of mood disorders and settings. (2) to examine the epidemiology of depression following a major social movement. We showed that childhood adversity and adulthood stressors were associated with depression and first-onset mania using the Guangzhou Biobank Cohort Study (n=9,729) and US National Epidemiologic Survey on Alcohol and Related Conditions (n=34,653), respectively. History of childhood adversity potentiated the association of adult stressors with depressive symptoms and first-onset mania. Our findings provide empirical support for the diathesis-stress model and stress sensitisation, and clarifies the relevance of these frameworks to mood disorders in general and the global population. Moreover, the association of maternal separation during childhood and depression among adults in Guangzhou could have implications to the 60 million “left-behind children” currently in China. Building upon these studies, we developed a research programme on the population determinants of depression in the FAMILY Cohort (n=46,001) in Hong Kong. This included the validation of resilience and other scales in the Hong Kong general population. Although the magnitude of Hong Kong’s Occupy Central/Umbrella Movement (OCUM) was unforeseen and unprecdented, our prior work with the FAMILY Cohort provided us with pre-event data and validated instruments to examine the mental health impact of the protests. To inform our studies on OCUM, we conducted a systematic review on social movements and depression. Our review showed that the mental health consequences of social movements were sparesly documented and remained unclear. Accordingly, we assessed the prevalence and longitudinal predictors of depressive sequelae following OCUM. A panel of FAMILY Cohort participants (n=909 and n=1,170) was interviewed at six time points: twice each before, during and after the OCUM. We showed that the absolute prevalence of probable depression increased by 7.0% six months after OCUM, regardless of personal involvement in the protests. Higher intra-familial socio-political conflict was associated with more depressive symptoms. We also identified four trajectories 14 months after OCUM: “resistant” (22.6% of sample), “resilient” (37.0%), “mild depressive symptoms” (32.5%), and “persistent moderate depression” (8.0%). Baseline predictors that appeared to protect against “persistent moderate depression” included higher household income, greater psychological resilience, more family harmony, higher family support, and better self-rated health. In conclusion, social movements can result in substantial and sustained depressive sequelae in the community, particularly among individuals lacking social support. Health care professionals therefore need to be vigilant of the mental health consequences of life course stress and social movements. Psychosocial interventions based on the diathesis-stress model could be promising in the prevention of mood disorders.