The Wall Street Journal By Melinda Beck The Wall Street Journal One of the most agonizing questions that parents of children with autism ask is—why? Now, a growing number of genetic tests are providing some answers.Melinda Beck on Lunch Break looks at how a growing number of genetic tests for autism are providing answers for some families. Plus, the parent of an autistic child joins us to explain how a new drug for the condition is having an impact on her son. Photo: Brian Harkin for The Wall Street Journal. Scientists say that roughly 20% of autism cases can be linked to known genetic abnormalities, and many more may be discovered.Pinpointing a genetic explanation can help predict whether siblings are likely to have the disorder—and even point to new, targeted treatments. Last week, for example, researchers reported that an experimental drug, arbaclofen, reduced social withdrawal and challenging behaviors in children and adults with Fragile X syndrome, the single most common genetic cause of autism.