The relationship between independent and dependent life events and depression symptoms in Sri Lanka: a twin and singleton study

Abstract

Purpose Life events have been associated with a variety of mental health conditions including depression. There is a scarcity of research in South Asia exploring the aetiology of independent and dependent life events and their relationship with depres sion symptoms. This study aimed, in a Sri Lankan population, to identify the socio-demographic correlates and genetic and environmental infuences on independent and dependent life events and their relationship with depression. Methods Questionnaire data came from the Colombo Twin and Singleton Follow-up Study, CoTaSS-2 (N=3969), a popula tion study of Sri Lankan twins and singletons. Lifetime-ever independent and dependent life events were measured using a questionnaire and depressive symptoms using the Revised Beck’s Depression Inventory. Structural Equation Model-ftting analyses explored the genetic and environmental infuences on life events and depression. Results Living in a rural environment and fnancial hardship were associated with greater reporting of independent and dependent life events. Sex diferences were evident in the aetiology of life events and depression symptoms. Independent and dependent life events, but not depression symptoms, were heritable in males. Independent life events and depression symptoms, but not dependent life events, were heritable in females. Non-shared environmental infuences explained phe notypic associations between independent life events and depression symptoms in both males and females. Genetic and non-shared environmental infuences explained the phenotypic associations between dependent life events and depression symptoms in males. Only non-shared environment explained the covariation between dependent life events and depression symptoms in females. Conclusions Socio-demographic correlates of independent and dependent life events were similar to those reported in Western populations. Life events were associated with increased depression symptoms. Contrary to research in Western populations, we found that non-shared environmental, rather than genetic, infuences explained much of the covariation between life events and depression symptoms. This suggests that whilst independent LEs may be heritable, the relationship is unlikely to be confounded by genetic infuences and has signifcant implications for possible interventions for depression. Keywords Life events · Depression · Sri Lanka · Twins · Genetics