How old was dad when the child was born?
Whether it is you or your child who is on the spectrum, how old was the father (yours or your child's) when the child was born?
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."