BACKGROUND: The offspring of parents with severe mental illness (SMI) are at higher risk of mortality and of developing certain somatic diseases. However, across the full spectrum of somatic illness, there remains a gap in knowledge regarding morbidity.

METHODS: We conducted a register-based nationwide cohort study of all 2 000 694 individuals born in Denmark between 1982 and 2012. Maximum age of offspring at follow-up was 30 years. Information on parents' psychiatric diagnoses of schizophrenia, bipolar disorder, and unipolar depression was retrieved from the Psychiatric Central Register. We estimated incidence rate ratio (IRR), cumulative incidence percentage and mortality rate ratio of first hospital contact for a broad spectrum of somatic illnesses according to the International Statistical Classification of Diseases and Related Health Problems. Analyses were adjusted for important confounders.

RESULTS: Offspring of individuals with SMI had higher risk of somatic hospital contacts IRR: 1.17 (95% CI: 1.16-1.18) with maternal depression being associated with the highest IRR (1.22, 95% CI: 1.20-1.24). Offspring of parents with SMI had higher risk within most broad diagnostic categories with highest IRRs for unclassified somatic diagnoses, infections and endocrine diseases ranging from 1.27 (95% CI: 1.25-1.28) to 1.26 (95% CI: 1.23-1.29) (all P < .0001). Morbidity was particularly increased in children aged 0-7 years. The mortality rate ratio associated with parental SMI was 1.31 (95% CI: 1.21-1.41) with excess mortality mainly due to unnatural causes.

CONCLUSION: Our findings indicate that offspring of parents with SMI experienced increased mortality and somatic morbidity warranting heightened vigilance and support for this population.