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Autism Research Roundup: Sibling and Diagnostic Substitution

As we tend to like to do here, this week we’re going to take a closer look at two of the news stories making the rounds in relation to the light they both shed on both the effect of age on autism risk and reasons behind the rise in autism diagnoses.

First off, the latest study from scientists at a Kaiser Permanente group in California, published in the journal Pediatrics, is putting forth the hypothesis that the time between the birth of one child and the conception of the next may actually affect the second child’s risk of developing autism. It’s quite common for studies to feature siblings who both have autism, a phenomenon that has in part been attributed to genetics, but one that now might be explained as a matter of time as well.

There have been two prior studies that found that either having kids closer together or widely spaced apart resulted in a 50% to two-fold increased risk of autism compared to children conceived 12 to 60 or 80 months after the birth of an older sibling, though it wasn’t clear if the association was driven by the spacing of time or additional factors.

However, following the most recent study, Lisa Croen and her team of researchers studied 45,261 children born in northern California between 2000 and 2009 and monitored for factors other than time, such as the mother’s weight before, during, and between pregnancies, the birth weight of the second baby, whether the second baby was porn premature, etc. But even with taking all of these many different factors into account, there still remained a clear and strong connection between both shorter and longer times between pregnancies and the risk of autism, which remained strong.

For children conceived less than 12 months or more than 72 months after the birth of an older sibling, the risk of autism was two to three fold higher than for those conceived 36 months to 47 months later. “We had the ability to look at a number of factors that might explain the findings and they actually didn’t explain them,” says Croen. “With all the data we had, we could not explain away what we found. So now we have to discover what it is about the short interval or long interval between pregnancies that increases the risk of autism in the second child.”

In other briefer science news, a new round of studies conducted in Sweden, Denmark, and the U.S. to better understand the cause behind the rise in autism diagnoses—which have grown from 1 in 150 children in 2000 to 1 in 68 in 2014—found that the cause does in fact lie in the diagnoses themselves rather than there being a rise in cases. Simply put, more children are being labeled as autistic where in the past, they might have just been seen as having a learning disability.

While this isn’t exactly groundbreaking news to frequent readers of this space, it does go a long way to raising awareness about autism and how we can better identify it in young children.