New research shows that children born to fathers over 45 are 13 times more likely to have ADHD and 25 times more likely to have bipolar disorder.

If you’re thinking about having children at a later age, you may want to reconsider that decision.

A new study published in JAMA Psychiatry suggests that fathers age 45 or older are at a higher risk of having children with psychiatric and academic problems.

Specifically, the study states that children born to 45-year-old fathers, compared with those born to 25-year-old fathers, are 25 times more likely to be bipolar and 13 times more likely to have ADHD. They are also 3.5 times more likely to have autism, 2.5 times more likely to have suicidal behavior or a substance abuse problem, and twice as likely to have a psychiatric disorder.

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Researchers at Indiana University and the Karolinska Institute in Stockholm came to this conclusion after examining the data of everyone born in Sweden from 1973 to 2001. They compared siblings and cousins, which accounts for outlying factors such as education and income.

“We were shocked by the findings,” lead author Brian D’Onofrio, associate professor in the Department of Psychological and Brain Sciences in the College of Arts and Sciences at IU Bloomington, said in a statement.

Previous research into the subject found that advanced paternal age may have diminished the rate at which these problems occur, but the new study suggests that these risks increase steadily.

There is no particular age where becoming a father is known to become problematic.

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While a woman is born with all of the eggs she could possibly use in her lifetime, men can continue to produce sperm their entire lives. Each new sperm that replicates runs a risk of carrying mutated DNA.

Previous research has shown that as men are exposed to numerous environmental toxins—such as air pollution, alcohol intake, and more—those toxins can affect sperm. Molecular genetics, researchers said, has shown that older men ten to have more genetic mutations in their sperm.

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Researchers, however, noted that we’re living in a new era of human history. In the not-too-distant past, when we were hunters and gatherers, men who lived to be 30 were considered elders, so procreating and spreading their genes was something that needed to be handled at a young age.

With advancements in medicine and improved standards of living, the average life expectancy for a man living in the U.S. is now 77 years. In 12 other countries, that age is over 80, according to the World Health Organization.

Over the past 40 years, the average age for childbearing has increased by four years. In 1970, women were more likely to have their first child at age 21.5, but that number is now 25.4. Men, on average, are having their first children at 28.

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Another emerging common trend has seen people waiting to have children until they are more financially and socially secure.

Given the known risks, D’Onofrio suggests that policy-makers should look to programs that help accommodate younger parents, so that they can have children earlier without having to set aside their professional goals.

“While the findings do not indicate that every child born to an older father will have these problems,” he said, “they add to a growing body of research indicating that advancing paternal age is associated with increased risk for serious problems. As such, the entire body of research can help to inform individuals in their personal and medical decision-making.”