Sibling spacing may be tied to autism risk: study - Reuters A new study suggests that kids who are born only a year or two after an older sibling might be more likely to be diagnosed with autism than those with a bigger age gap. The study does not prove that spacing children closer together causes autism in the second sibling, and Cheslack-Postava said there are many possible ways to explain the link - and that she "can't speculate as to what's the most likely." "There's one possible explanation, (which) is that there is some biological factor" such as a mother's nutrient levels or stress that makes a second child more at risk for autism when siblings are closely spaced, Dr. Keely Cheslack-Postava, the study's lead author, from Columbia University, told Reuters Health. The trend could, however, be explained by social factors, Cheslack-Postava said. Parents may be more likely to take a younger sibling to the doctor to be checked out for autism if they remember that only a year or two ago, when their older sibling was the same age, he or she was much farther along in development in certain areas.