Widowhood and the Stability of Late Life Depressive Symptomatology in the Swedish Adoption Twin Study of Aging

How nonshared environmental factors come to correlate with heredity

Conventional longitudinal behavioral genetic models estimate the relative contribution of genetic and environmental factors to stability and change of traits and behaviors. Longitudinal models rarely explain the processes that generate observed differences between genetically and socially related individuals. We propose that exchanges between individuals and their environments (i.e., phenotype-environment effects) can explain the emergence of observed differences over time. Phenotype-environment models, however, would require violation of the independence assumption of standard behavioral genetic models; that is, uncorrelated genetic and environmental factors. We review how specification of phenotype-environment effects contributes to understanding observed changes in genetic variability over time and longitudinal correlations among nonshared environmental factors. We then provide an example using 30 days of positive and negative affect scores from an all-female sample of twins. Results demonstrate that the phenotype-environment effects explain how heritability estimates fluctuate as well as how nonshared environmental factors persist over time. We discuss possible mechanisms underlying change in gene-environment correlation over time, the advantages and challenges of including gene-environment correlation in longitudinal twin models, and recommendations for future research.

Trajectories of depression symptoms in Chinese elderly during widowhood: a secondary analysis

Objectives: This study aims to identify heterogeneous depressive symptom trajectories among the widowed elderly in China, to explore predictive variables of latent class membership, and to detect between-classes differences in life satisfaction across time.Method: Data of 198 individuals widowed between 2011 and 2013 were drawn from The China Health and Retirement Longitudinal Study (CHARLS), a nationally representative survey. Latent class growth analysis was employed to identify depressive symptom trajectories across 2011, 2013, and 2015, and a three-step auxiliary approach was applied to detect predictive variables of latent class membership. Mixed Analysis of Variances was followed to make between-class comparisons on life satisfaction across time.Results: Four grieving trajectories were identified: resilient (54.6%), chronic grief (23.7%), depressed-improved (11.6%), and chronic depression (10.1%). Older age, living exclusively with spouse before widowhood, and agricultural Hukou were significant predictors of depressed-improved, chronic grief, and chronic depression patterns, respectively. Life satisfaction in all groups except for the resilient one remained stable across time, and that of the chronic depression group was significantly lower than those of all the remaining groups.Conclusion: Consistent depressive symptom trajectories during late-life widowhood exist across nations while the specific culture, values, and resources in the Chinese context may have contributed to a particularly high proportion of the chronic grief trajectory. More efforts should be made to identify patterns with predictors before support are provided, and interventions need to be tailored to target specific needs in each subgroup of the elderly during their transitions to widowhood.

Incidence, risk, and associated factors of depression in adults with physical and sensory disabilities: A nationwide population-based study

BACKGROUND

Physical disability has been associated with the risk of depression. We examined the incidence, risk, and associated factors of depression in Taiwanese adults with physical/sensory disabilities.

METHODS

Two national databases were used to retrospectively analyze 749,491 ≥20-year-old Taiwanese with physical/sensory disabilities in 2002-2008. The incidence of depression was analyzed by univariate Poisson regression. Risk factors of depression were followed up through 2014 and examined with a Cox proportional hazards model.

RESULTS

Among the study subjects, the incidence of depression was 6.29 per 1000 person-years, with 1.83 per 1000 person-years corresponding to major depression. The subjects' depression risk was affected by disability type, disability severity, gender, age, education, marital status, aboriginal status, monthly salary, residence urbanization level, and Charlson comorbidity index (CCI). Subjects with rare diseases, mild disability, female gender, age 35-44 years, a high school education level, divorced/widowed status, non-aboriginal status, a NT$22,801-28,800 monthly salary, a highly urbanized residence area, or a CCI≥3 were at higher risk for depression.

CONCLUSIONS AND IMPLICATIONS

Adults with physical/sensory disabilities have a 3.7-fold higher incidence of depression than the general population. Social services departments and family members should take extra measures toward preventing and treating depression in this subpopulation.

Twin Differentiation of Cognitive Ability Through Phenotype to Environment Transmission: The Louisville Twin Study

The Louisville Twin Study is one of the most intensive twin studies of cognitive ability. The repeated measurements of the twins are ideal for testing developmental twin models that allow for the accumulation of gene-environment correlation via a (P⇒E) transmission process to explain twins' divergence in mean ability level over time. Using full-scale IQ scores from 566 pairs of twins (MZ = 278; DZ = 288), we tested whether a P⇒E transmission model provided better representation of actual developmental processes than a genetic simplex model. We also addressed whether the induced gene-environment correlation alters the meaning of the latent nonshared environmental factors with a simple numerical method for interpreting nonshared environmental factors in the context of P⇒E transmission. The results suggest that a P⇒E model provided better fit to twins' FSIQ data than a genetic simplex model and the meaning of the nonshared environment was preserved in the context of P⇒E.