To Örebro University

Background: Evidence has emerged indicating a role of stress-related disorders in the development of autoimmune diseases. However, it remains unknown whether genetic components contribute to the observed association. We therefore investigated the co-aggregation of stress-related disorders and autoimmune diseases in individuals and their family members in the Swedish population.

Methods: We identified 4,123,631 individuals born in Sweden between 1953 and 1993. Based on information from the Multi-Generation Register, we conducted cohorts of relatives of varying relatedness. Logistic regression was used to estimate the association between clinical ascertained stress-related disorders (i.e., acute stress reaction, posttraumatic stress disorder [PTSD], adjustment disorder, and other severe stress reactions) and autoimmune diseases (36 different types) in individuals and in families, presenting relative risks as odds ratios (ORs).

Results: Individuals with stress-related disorder were at high er risk of having autoimmune diseases compared with individuals who did nothave stress-related disorder (OR = 1.66, 95% confidence intervals (CI) 1.63–1.69). Within families, the association seemed strongest between monozygotic twins (OR = 1.47, 95% CI 1.07–2.03), and then decreased with descending dyads of familial/genetic relatedness ̄OR was 1.28 (95% CI 0.97–1.67), 1.16 (95% CI 1.14–1.18), 1.05 (95% CI 1.02–1.09), 1.06 (95% CI 1.03–1.10), 1.05 (95% CI 1.04–1.06), and 1.00 (95% CI 0.98–1.04) for dizygotic twins, full siblings, maternal half siblings, paternal half siblings, full cousins, and half cousins, respectively. Further analyses on PTSD and autoimmune diseases obtained similar estimates.

Conclusion: The pattern of the association across twin zygosity and varying familial relatedness supports the hypothesis of a genetic overlap between stress-related disorders and autoimmune diseases which warrants further exploration.