A comprehensive assessment of parental age and psychiatric disorders.

Importance: There has been recent interest in the findings that the offspring of older fathers have an increased risk of both de novo mutations and neuropsychiatric disorders. However, the offspring of younger parents are also at risk for some adverse mental health outcomes.

Objective: To determine the association between maternal and paternal age and a comprehensive range of mental health disorders.

Design, Setting, And Participants: A comprehensive, population-based record linkage study using the Danish Psychiatric Central Research Register from January 1, 1995, through December 31, 2011. A total of 2 894 688 persons born in Denmark from January 1, 1955, through December 31, 2006, were followed up during the study period.

Exposures: Maternal and paternal age at the time of offspring's birth.

Main Outcomes And Measures: We examined a broad range of International Classification of Diseases-defined mental disorders, including substance use; schizophrenia and related disorders; mood disorders; neurotic, stress-related, and somatoform disorders; eating disorders; specific personality disorders; and a range of developmental and childhood disorders. The incidence rate ratios for each mental disorder outcome were estimated by log linear Poisson regression with adjustments for the calendar period, age, sex, and age of the other parent.

Results: The cohort was observed for 42.7 million person-years, during which 218 441 members of the cohort had their first psychiatric contact for any psychiatric disorder. Based on the overall risk of psychiatric disorders, the offspring of younger and older parents were at increased risk compared with those of parents aged 25 to 29 years. When the offspring were examined for particular disorders, the nature of the relationship changed. For example, the offspring of older fathers were at an increased risk of schizophrenia and related disorders, mental retardation, and autism spectrum disorders. In contrast, the offspring of young mothers (and to a lesser extent young fathers) were at an increased risk for substance use disorders, hyperkinetic disorders, and mental retardation.

Conclusions And Relevance: The offspring of younger mothers and older fathers are at risk for different mental health disorders. These differences can provide clues to the complex risk architecture underpinning the association between parental age and the mental health of offspring.