When Lisa and Tim Flannery's son, Braedan, was diagnosed with autism at 18 months old, they immediately started occupational and speech therapy."He'd cross all his fingers, wouldn't make eye contact," said Lisa Flannery. "He would scream if he wanted something."Questions about what caused the disease still loom large for this Roxborough family."It's been hard for us," she said.Now, they've enrolled him in the national's largest study of risk factors for autism, the Study to Explore Early Development or SEED.The University of Colorado Denver is taking part in the research, a multi-year study funded by the Centers for Disease Control and Prevention."Nobody really knows right now what the causes are. The more we know about the risk factors, the more we can know the causes," said Kristina Hightshoe, the SEED study coordinator. "We hope this is a breakthrough study."Researchers are collecting data from hundreds of families with autistic children, from genetic tests to immunization history to environmental factors."For example, we're collecting hair samples looking for metal content," said Hightshoe.Psychologist Susan Hepburn with UC Denver said the results will help answer questions about why there has been such an increase in autism and better define autism to help prevent misdiagnosis."I absolutely think that what we think about autism is going to change. I think we'll discover that what were currently describing as one condition can actually be sub-typed into several different conditions," said Hepburn.Autism is a complex disorder.Researchers for the SEED study want to learn more about how the children think, grow and interact with the world around them. They're also studying other health problems commonly found in children with autism.The Flannerys said they hope the research will help other families avoid what they've gone through and help them better understand the disorder thats changed so many lives."Like any parent, we just want to do what we can for our kids," said Tim Flannery. Researchers are hoping to enroll more families with children ages 2 to 5 in the study.They will keep gathering data until this summer and then start analyzing it.