he strongest support for a genetic influence on autism is that Group of answer choices autism is effectively treated using serotonin agonist drugs. the concordance rate for autism is 5 percent in fraternal twins and 70 percent in identical twins. siblings of autistic children are less likely to develop autism than the normal population. parents of autistic children are usually autistic. the concordance rate for autism is 70 percent in fraternal twins and 0 percent in identical twins.