Cue another theory in the elusive search for the causes of autism: having children spaced too closely together. Researchers have discovered a risk that's apparently small, but significant—about 0.76% for children conceived less than a year after a sibling, versus 0.47% overall—based on a study of more than 600,000 California children born from 1992 and 2002, reports AP.
"That was pretty shocking to us, to be honest," said an author of the reserach paper. "No matter what we did, whether we were looking at autism severity, looking at age, or looking at all the various dimensions we could think of, we couldn't get rid of this finding." The study's authors were cautious about what conclusions to draw from their paper, hypothesizing it could be biological, it could relate to different diagnosis rates, or any combination of factors.