Family aggregation of mental disorders in the nationwide Danish three generation study

Objective: The study of familial aggregation of major mental disorders in a national population. Method: Within a Danish register-based cohort study, aggregation of mental disorders was analysed in all case-probands with first psychiatric contact before the age of 19years in the time period between 1 April 1969 and 29 June 2004 followed up until the age of 35years, their first-degree relatives, and a matched group of control-probands including their first-degree relatives. Results: Hazard rate ratios were significantly elevated for cases as compared to controls for all diagnoses among probands, parents, and siblings. Among children of the probands, these ratios were significantly elevated for neurotic (anxiety) disorders, mental retardation, developmental disorders, behavioural and emotional disorders of childhood and adolescence, and miscellaneous disorders. Family aggregation of any diagnosis was significantly higher in probands with substance use disorder, schizophrenia, affective disorders, neurotic (anxiety) disorders, and miscellaneous disorders. There was specificity of familial transmission for affective and neurotic (anxiety) disorders. Conclusion: This large nationwide study found some differential patterns of familial aggregation of major mental disorder