TIME mental health

More Bad News for Older Dads: Higher Risk of Kids With Mental Illness

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The effect of paternal age on autism, schizophrenia, and ADHD may be greater than previously thought

For so long, mothers – particularly older moms — bore the brunt of responsibility for genetic disorders in their children. And for good reason. Eggs are stockpiled from birth, not made anew with each monthly reproductive cycle, so eggs stored for decades until childbearing can develop genetic mutations. The older the mother, the greater the chance of abnormalities that can contribute to conditions such as Down syndrome, especially after age 35. Fathers, on the other hand, constantly make sperm, so their reproductive contribution was supposed to be fresher and free of accumulated DNA damage.

That may not actually be the case, however, according to the latest study in JAMA Psychiatry investigating how advanced paternal age can affect rates of mental illness and school performance in children. After a groundbreaking genetic analysis in 2012 highlighted the surprising number of spontaneous mutations that can occur in the sperm of older men, scientists have been delving into the relationship to better quantify and describe the risk. While some studies confirmed the connection, others failed to find a link.

MORE: Older Fathers Linked to Kids’ Autism and Schizophrenia Risk

In the latest research, Brian D’Onofrio, associate professor of psychological and brain sciences at Indiana University, and his colleagues attempted to address one of the biggest problems with studying the trend. Most of the previous investigations compared younger fathers and their children to different older fathers and their offspring. “That’s comparing apples and oranges,” says D’Onofrio. “We know young fathers and old fathers vary on many things.”

So his team turned to birth registry data from Sweden and compared children born to the same fathers, evaluating the siblings on various mental health and academic measures. The study included 2.6 million children born to 1.4 million fathers.

What they found surprised them – so much so that they spent about two months re-evaluating the data to make sure their numbers were correct. While the previous genetic study found that an older father’s DNA may account for about 15% of autism cases, D’Onofrio’s group found that the increased risk for children of fathers older than 45 years soared to 3.5 times compared to that of younger fathers. Children of older fathers also showed a 13 fold higher risk of developing attention deficit-hyperactivity disorder (ADHD), a 25 times greater chance of getting bipolar disorder, and twice the risk of developing a psychosis. These kids also had doubled risk of having a substance abuse problem and a 60% higher likelihood of getting failing grades in school compared with those with younger fathers.

MORE: Too Old to Be a Dad?

“What this study suggests is that the specific effect of older paternal age may actually be worse than we originally thought,” says D’Onofrio.

The scientists controlled for some of the well-known factors that can account for poor grades and psychoses and mental illnesses, such as the child’s birth order, the mother’s age, the mother’s and father’s education level, their history of psychiatric problems, and their history of criminality. Even after adjusting for these possible effects, they still found a strong correlation between higher rates of mental illness among younger siblings compared with their older ones.

The 2012 genetic study pointed to a possible reason for the higher rates of mental illnesses – because genetic mutations tend to accumulate each time a cell divides, older men may build up more spontaneous, or de novo, changes each time the sperm’s DNA is copied. While a 25-year-old father may pass on an average of 25 mutations to his child, a 40-year-old dad may bequeath each offspring as many as 65; the researchers calculated that the de novo mutation rate doubled with every 16.5 years of the father’s age. In contrast, regardless of her age, a mother tends to pass on about 15 mutations via her eggs.

The findings still need to be repeated by other groups, but the large sample size and the careful way that the researchers designed the study – to analyze the same fathers over time – suggest that the association is significant and worth considering for those who put off having a family. “This study suggests that paternal age does need to be considered as one of many risk factors associated with children’s mental health,” says D’Onofrio.

MORE: Fewer Drugs Being Prescribed to Treat Mental Illness Among Kids

Whether it gains the same amount of weight that maternal age does in family planning decisions isn’t clear yet, but even if it is confirmed, he notes that the correlation doesn’t predict that every child born to an older father will develop a mental illness. Older parents also have protective factors against these disorders, including more maturity and financial and social stability, that can offset some of the effect.

TIME Evolution

Did Miserably Wintry Weather Give Humans a Thirst for Milk?

Spilt Milk
Christopher T Stein / Getty Images

Geneticists find new clues in mankind's sudden and mysterious love of milk

Somewhere in the course of human evolution, our European ancestors learned to stop loathing lactose and love the udder, and a new study sheds light on our sudden and mysterious love of milk.

NPR reports that geneticists in Sweden have traced the love story back to recent history. Even though one-third of Spaniards are more than a little tolerant of lactose (Manchego is exhibit A), geneticists found lactose intolerant genes in the bones of their ancestors just 5,000 years ago.

In other words, Spaniards seem to have experienced a sudden burst of lactose love, and this finding pokes a hole in a competing theory of our evolution. It was hypothesized that lactose tolerance spread among sun — starved Europeans in the north, hungry for vitamin D. They got their fix of D from cow’s milk, and the more milk they could digest, the more they thrived. So why would the gene proliferate in sun-drenched regions of the South?

Good question, and for scientists hard on the case, the plot has just thickened.

[NPR]

MONEY health

DNA Testing: Crack Open Your Genetic Code

Genetic testing is getting cheaper and easier. What you should know before you use it.

For as little as $100, here are some secrets you can unlock from your DNA: Whether you could have inherited a risk factor for certain kinds of cancer. Or how much of your genetic makeup comes from Neanderthals.

You might also learn whether your genes raise your chances of getting diabetes — but your doctor will still probably be more interested in other, more obvious risk factors, such as your family history and diet.

In short, although technology is quickly making it cheaper and easier to get data about yourself, it’s not always clear which information is worth getting and which isn’t.

Here’s a guide to using, and paying for, genetic tests.

What you can find out — and what you’ll pay

Roughly, two kinds of tests are available.

The first is ordered by a doctor and will often involve finding all the variations in specific genes. Research has found some variations that point to a higher risk of diseases, including breast cancer and a kind of colon cancer.

A doctor might recommend a screen based on risk factors like family history or ethnic background. Other tests, says David Fleming, an internist and health ethicist at the University of Missouri, can provide clues to how you’ll respond to certain drugs or treatments.

The tests can cost $300 to $3,500. If your doctor recommends it, insurance will generally cover it like any other test. But call your insurer first: Some might require an advance letter from your doctor or a visit to a genetic counselor, a professional trained to help people use genetic information to manage their health.

The second kind of test is a home kit that lets you mail in a saliva sample and log on to a website to get results. It’s generally not covered by insurance. (The Food and Drug Administration has said it’s concerned about unregulated consumer tests but allowed companies to keep them on the market if they began the process of getting approval; none are yet FDA approved.)

One big player, 23andMe, has made a publicity splash by cutting its price to $99 for a report on up to 250 indicators, from that Neanderthal DNA to markers of health risk. This test may differ from one your doctor would order; it won’t read all the variations in a gene but looks for common markers.

For concerns about a specific disease, use a doctor, not a kit.

Why you shouldn’t face the serious stuff alone

Experts caution that the results of tests can be difficult to interpret on your own. That’s fine if you are looking for fun info on your ancestry. But discuss with a counselor or doctor in advance whether you should do a screen for a disease, and what a positive or negative result would mean.

You also need to think about what you’ll do if you get a worrying result.

A test can find markers of an elevated risk for late-onset Alzheimer’s, for example, but you can have them and never get the disease. And since there’s little to do now to prevent Alzheimer’s, you may feel better off not knowing.

Other screens, such as those for cancer, could leave you with difficult choices about how aggressively to respond. “The issue is when we make decisions based on fear rather than what we know,” says Fleming.

You’ll want professional help to sort through the facts. Visits to genetic counselors are often covered by insurers and billed like doctor’s visits. You can find a counselor at nsgc.org.

What tests don’t tell you

With some diseases, such as diabetes, it may be more accurate to simply look at your own family history, says Michael Dougherty, director of education at the American Society of Human Genetics. What’s more, he adds, “the genetic test doesn’t take into consideration all of the environmental factors.”

So it’s a good idea to eat right and exercise no matter what the result.

How safe are your records?

A law passed in 2008 prevents health insurers from using genetic information against you. Employers can’t use it either. But federal law doesn’t offer the same protection on long-term-care, life, and disability coverage. (Some states have stricter rules.)

“The concern is the insurance company could require you to show certain medical records,” says Harvard Medical School geneticist Robert Green. Or even just ask if you’ve been tested. It doesn’t appear to be happening yet, but it’s one more thing to keep in mind as you weigh whether you want to see what’s written in your DNA.

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