A new study from researchers at Indiana University in Bloomington, published in the journal JAMA Psychiatry, suggests that the children of older fathers may be more at risk of developing psychiatric problems than children born to younger fathers.
Previously, studies have indicated that "advancing paternal age" (APA) at childbearing is associated with increased risk of autism spectrum disorders (ASDs), schizophrenia and bipolar disorder, as well as academic and intellectual problems.
More recent genetic studies have claimed that the age of the father at conception is linked to the likelihood of "de novo mutations" developing in their children. De novo mutations are when a gene becomes present in a family for the first time as the result of a mutation in the egg or sperm from one of the parents.
These de novo mutations have also been linked to ASDs. Medical News Today reported on one genetic study that found this in 2012.
But a comprehensive study looking at the overall associations of psychiatric problems and APA has not been attempted until now.
New study compared siblings born in Sweden over a 28-year period
This was a large population-based study that looked at all people born in Sweden over a 28-year period, from 1973 to 2001. To test how much of an influence the age of the father at conception was, the researchers compared children who had been born to older fathers with their older siblings - children who were born when the same father was younger.
After comparing family members, the researchers estimated risk for the following:
- Attention-deficit/hyperactivity disorder
- Bipolar disorder
- Suicide attempt
- Substance abuse
- Low educational attainment.
They found that children born to fathers 45 years or older were at higher risk of developing all of these problems, compared with their siblings who were born when their fathers were between 20 and 24 years old.
Because the study examined siblings, the researchers ruled out genetic and environmental influences that could have caused one child to be more at risk of developing a psychiatric problem than another.
But these sibling-based comparison studies do have limitations and can provide some unreliable data.
For instance, the order in which different siblings are born could have an influence on their psychological development. This type of study also assumes that all of the children in a family are exposed to the same conditions growing up, when this might not be the case.
However, the researchers feel confident that their sibling-comparison results are consistent with the theory that genetic mutations caused by APA during fertilization are responsible for increased risk of psychiatric problems.
"The findings suggest that APA represents a risk of numerous public health and societal problems. Regardless of whether these results should lead to policy changes, clarification of the associations with APA would inform future basic neuroscience research, medical practice and personal decision-making about childbearing."