John McGrath, M.D., of the University of Queensland in Australia and colleagues used records from the Danish Psychiatric Central Research Register to follow 2,894,688 individuals born in Denmark from January 1, 1955, through December 31, 2006. They examined incidence of a broad range of mental disorders and maternal and paternal age at birth. A total of 218,441 members of the cohort had a first psychiatric contact for any psychiatric disorder during the study period. Based on the overall risk of developing psychiatric disorders, the offspring of both younger and older parents were at increased risk compared with those of parents aged 25 to 29.
Compared with the offspring of mothers aged 25 to 29, the offspring of mothers aged 12 to 19 had a 51% increased risk of having a mental disorder; no significantly increased risk for the offspring of older mothers was found. In contrast, paternal age showed a U-shaped relationship, with the offspring of teenaged fathers having a 28% increased risk for a psychiatric disorder, whereas the offspring of the fathers aged 45 or older had a 34% increased risk.
Interestingly, different disorders were associated with different parental age extremes. For example, the offspring of older fathers were at increased risk for 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, according to the report. “These differences can provide clues to the complex risk architecture underpinning the association between parental age and the mental health of offspring,” the researchers said.
For more information on this subject, see the Psychiatric News article, “Gene Mutation Explains Link of Paternal Age, Mental Illness." Also see the American Journal of Psychiatry study, “Selfish Spermatogonial Selection”: A Novel Mechanism for the Association Between Advanced Paternal Age and Neurodevelopmental Disorders."