Objectives: The widely acknowledged negative association between social isolation and physical and mental health is commonly interpreted in terms of social causation and has served as an important frame of reference for many interventions. However, evidence of social causation is likely biased because most studies cannot differentiate between social causation and health selection. The public attention given to this field of research indicates a need for analytical strategies that improve the understanding of the underlying link between social isolation and physical and mental health.
Methods: Using data from the German Socio-Economic Panel (GSOEP) study (2004 to 2012) of 6740 men and 7189 women aged 50 and above, we estimated dynamic panel models with fixed effects that allow us to probe the social causation hypothesis while accounting for direct selection (reverse causality) and indirect selection (unobserved heterogeneity). All analyses were conducted for women and men separately.
Results: We found that social isolation adversely affected mental health among older men and women to a degree that suggests practical relevance. However, we could not find a similar effect on physical health. A considerable part of the association between social isolation and both health outcomes was attributable to indirect selection, whereas direct selection led to underestimating the relevance of social isolation for mental health.
Conclusion: The results provide more convincing evidence that social isolation has adverse effects on mental health among older people. We conclude that effective interventions targeting social isolation might indeed be suitable for improving mental health among older people.
Keywords: Social isolation; fixed-effects regression; health; panel data; structural equation modeling.