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

Stressful Life Events and Neuroticism among Chinese Women with Recurrent Major Depressive Disorder

BACKGROUND

Depression is associated with a high incidence of stressful life events (SLEs) and neuroticism. However, the impact of SLEs and neuroticism on the recurrence of major depressive disorder (MDD) remains unclear. Therefore, we aimed to identify the potential causal relationship between SLEs, neuroticism, and depression recurrence.

METHODS

This study included 5561 female patients with recurrent MDD (ages 30-60) and 4257 healthy volunteers (ages 40-60) from the China, Oxford, and Virginia Commonwealth University Experimental Research on Genetic Epidemiology (CONVERGE) study. We compared the female patients with recurrent MDD to a gender and age-matched group of healthy volunteers. Odds ratios (ORs) were calculated using logistic regression analysis to assess the impact of SLEs on depression onset. Furthermore, we employed bootstrapping sampling procedures to explore the mediating role of neuroticism between SLEs and the number of depressive episodes.

RESULTS

SLEs contributed to the occurrence of major depression, with rape (OR = 19.14, p = 0.004), serious neglect (OR = 3.65, p < 0.001), legal problems (OR = 2.51, p < 0.001), and divorce or relationship breakup (OR = 2.14, p < 0.001) being significantly associated with the onset of MDD. Following MDD onset, certain SLEs, such as the death of a family member (Z = 3.64, p < 0.001), unemployment (Z = 5.63, p < 0.001), job termination (Z = 6.43, p < 0.001), and financial crisis (Z = 5.53, p < 0.001), led to a significant increase in the number of depressive episodes. Furthermore, mediation analysis demonstrated that events such as divorce or relationship breakup (p < 0.05), rape (p < 0.05), financial crisis (p < 0.05), and physical abuse (p < 0.05) indirectly affected the number of depressive episodes through neuroticism.

CONCLUSIONS

Our study demonstrates that SLEs in different categories have different effects on the onset and recurrence of MDD, and their effects regarding personal maltreatment, interpersonal relationship, and finance on the recurrence of depression are mediated by neuroticism.

Associations between socioeconomic factors and depression in Sri Lanka: The role of gene-environment interplay

BACKGROUND

Low socioeconomic status is a risk factor for depression. The nature and magnitude of associations can differ cross-culturally and is influenced by a range of contextual factors. We examined the aetiology of socioeconomic indicators and depression symptoms and investigated whether socioeconomic indicators moderate genetic and environmental influences on depression symptoms in a Sri Lankan population.

METHODS

Data were from a population-based sample of twins (N = 2934) and singletons (N = 1035) in Colombo, Sri Lanka. Standard of living, educational attainment, and financial strain were used to index socioeconomic status. Depression symptoms were assessed using the Revised Beck Depression Inventory. Structural equation modelling explored genetic and environmental influences on socioeconomic indicators and depression symptoms and moderation of aetiological influences on depression symptoms by socioeconomic status.

RESULTS

Depression symptoms were associated with lower standard of living, lower educational attainment, and financial strain. Sex differences were evident in the aetiology of standard of living, with a small contribution of genetic influences in females. Educational attainment was moderately heritable in both males and females. Total variance in depression was greater among less socioeconomically advantaged individuals. Modest evidence of moderation of the aetiology of depression by standard of living and education was observed.

LIMITATIONS

While the sample is representative of individuals living in Colombo District, it may not be representative of different regions of Sri Lanka.

CONCLUSIONS

The aetiology of depression varies across socioeconomic contexts, suggesting a potential mechanism through which socioeconomic disadvantage increases the risk for depression in Sri Lanka. Findings have implications for cross-cultural investigations of the role of socioeconomic factors in depression and for identifying targets for social interventions.

Annual Research Review: Towards a deeper understanding of nature and nurture: combining family-based quasi-experimental methods with genomic data

Distinguishing between the effects of nature and nurture constitutes a major research goal for those interested in understanding human development. It is known, for example, that many parent traits predict mental health outcomes in children, but the causal processes underlying such associations are often unclear. Family-based quasi-experimental designs such as sibling comparison, adoption and extended family studies have been used for decades to distinguish the genetic transmission of risk from the environmental effects family members potentially have on one another. Recently, these designs have been combined with genomic data, and this combination is fuelling a range of exciting methodological advances. In this review we explore these advances - highlighting the ways in which they have been applied to date and considering what they are likely to teach us in the coming years about the aetiology and intergenerational transmission of psychopathology.

The aetiological relationship between depressive symptoms and health-related quality of life: A population-based twin study in Sri Lanka

Objective

Depression often co-occurs with poor health-related quality of life (HRQL). Twin studies report genetic and individual-level environmental underpinnings in the aetiology of both depression and HRQL, but there is limited twin research exploring this association further. There is also little evidence on sex differences and non-Western populations are underrepresented. In this paper we explored the phenotypic and aetiological relationship between depressive symptoms and HRQL and possible sex differences in a low-middle-income Sri Lankan population.

Method

Data for 3,948 participants came from the Colombo Twin and Singleton Follow-up Study (CoTaSS-2). Using self-report measures of depressive symptoms and HRQL, we conducted univariate and bivariate sex-limitation twin analyses.

Results

Depressive symptoms showed moderate genetic (33%) and strong nonshared environmental influences (67%). Nonshared environment accounted for the majority of variance in all the subscales of HRQL (ranging from 68 to 93%), alongside small genetic influences (ranging from 0 to 23%) and shared environmental influences (ranging from 0 to 28%). Genetic influences were significant for emotional wellbeing (23%). Shared environmental influences were significant for four out of the eight HRQL variables (ranging from 22–28%), and they were more prominent in females than males. Depressive symptoms were significantly associated with lower HRQL scores. These correlations were mostly explained by overlapping nonshared environmental effects. For traits related to emotional functioning, we also detected substantial overlapping genetic influences with depressive symptoms.

Conclusions

Our study confirmed previous findings of a negative association between depressive symptoms and HRQL. However, some of the aetiological factors of HRQL differed from Western studies, particularly regarding the effects of shared environment. Our findings highlight the importance of cross-cultural research in understanding associations between psychological wellbeing and HRQL.

Relationship between CRP and depression: A genetically sensitive study in Sri Lanka

BACKGROUND

Previous studies have shown associations between major depression and C-reactive protein (CRP) levels. Few studies have considered the extent to which shared genetic and environmental factors contribute to this association, nor have they considered the relationship outside of European populations. We examined the association between CRP levels and depression and their aetiology in a Sri Lankan population.

METHODS

Data were collected from 2577 twins and 899 singletons in Colombo, Sri Lanka. Depression symptoms were assessed using the revised Beck Depression Inventory (BDI-II). High-sensitive CRP blood levels were assessed using immunoturbidimetry. Linear regressions were performed to test the association between CRP and depression. The heritability of CRP levels was estimated using Structural Equation Modelling.

RESULTS

CRP was significantly associated with BMI (p < 0.01) but not depression (p > 0.05). In males, variance in CRP levels was explained by shared environment (51% 95%CIs: 13-62) and non-shared environment (45% 95%CIs: 36-54). In contrast, in females, CRP variance was explained by genetic (41% 95%CIs: 10-52) and non-shared environment (56% 95%CIs: 47-67). A genetic correlation between CRP and BMI was observed in females only.

LIMITATIONS

CRP level was based on a single data collection point, longer term data collection would give a more accurate picture of an individual's state of inflammation.

CONCLUSIONS

The lack of association between depression and CRP strengthens the hypothesis that inflammation might contribute to the development of some, but not all types of depression. CRP levels were moderated by the environment, suggesting interventions aimed at reducing CRP levels and risk for inflammatory conditions, particularly in males.