A large Swedish study finds that the risk of many psychiatric disorders is higher in children born to older fathers. The findings extend those of earlier studies linking higher autism risk to older dads. The new study appears online this week in JAMA Psychiatry.

The researchers analyzed health records for everyone born in Sweden from 1973 to 2001. They found a strong association between a father’s age at childbearing and disorders including autism, ADHD, bipolar disorder, schizophrenia, substance abuse problems and low IQ.

For most of these disorders, the likelihood of the disorder increased steadily with paternal age. When compared to a child born to a 24-year-old father, a child born to a 45-year-old father was 3.5 times more likely to have autism, 13 times more likely to have ADHD and 25 times more likely to have bipolar disorder.

“Research is consistently finding that advanced parental age is a risk factor for autism, but it should not be interpreted as placing blame on parents,” comments epidemiologist Michael Rosanoff, Autism Speaks associated director for public health research. “Older parents are at higher risk of having a child with developmental challenges in general, likely due to common underlying mechanisms.”

Rosanoff emphasizes that the increase in autism risk is relatively modest. The vast majority of children born to older fathers will not have any of these disorders, he notes. And most children who have autism are born to younger parents – because earlier child bearing is much more common.

Earlier research on paternal age and autism noted that older fathers have more mutations in the germ cells that produce sperm. This may increase the likelihood that a mutation disrupts one or more genes vital to brain development.

For more perspective, see “Father’s Age Linked to Increased Genetic Mutations in Children,” “Genes, Older Dads and Autism,” “Risk Versus Cause” and “Many Tiny Mutations May Contribute to Autism.”