Genetic propensity to mental health traits and their associations with social connection phenotypes: evidence from the English Longitudinal Study of Ageing

There is a wealth of phenotypic literature on the interplay between mental health and social connections. However, how genetic propensity to mental health traits may be associated with distinct social connections phenotypes (i.e., structural, functional and quality aspects) is largely unexplored. Using polygenic scores (PGSs), we explored the associations between genetic propensity for five mental health traits (PGSdepressive-symptoms, PGSanxiety, PGSbipolar- disorder, PGSschizophrenia, PGSwellbeing) and four social connection phenotypes (social isolation, loneliness, social support and relationship strain). Linear regressions were conducted in a representative sample of unrelated older adults living in the UK, and analyses were controlled for age, sex, and principal components to account for population stratification. The results show that higher PGSdepressive-symptoms was associated with greater loneliness (B=0.11, CI-95%=0.07, 0.15) and relationship strain (B=0.09, CI-95%=0.05, 0.13) and lower social support (B=-0.07, CI-95%=-0.13, -0.01). Higher PGSanxiety was associated with higher social isolation (B=0.05, CI-95%=0.00, 0.10) and greater relationship strain (B=0.05, CI-95%=0.01, 0.09). Higher PGSbipolar-disorder was associated with greater loneliness (B=0.05, CI-95%=0.01, 0.09) and relationship strain (B=0.06, CI-95%=0.02, 0.10). Higher PGSwellbeing was associated with lower loneliness (B=-0.07, CI-95%=-0.11, -0.03), relationship strain (B=- 0.07, CI-95%=-0.11, -0.03), and social isolation (B=-0.07, CI-95%=-0.12, -0.02), and greater social support (B=0.14, CI-95%=0.08, 0.21). This suggests differential associations between different mental health PGSs and distinct aspects of social connections, indicating a nuanced picture. Our findings confirm that genetics play a role in having adequate social connections, which can be supported through social, community, and cultural schemes. They also highlight that genetic confounding is important when using observational data assessing the associations between mental health and social connections.