Autism can likely develop when low birth weight babies are combined with other factors such as environment and genetic predisposition, new research suggests. Researchers from the University of Pennsylvania School of Nursing and School of Medicine identified 1,105 children who weighed less than 2,000 grams at birth between Oct. 1, 1984, and July 3, 1989. Sixteen years later, researchers were able to reach 623 of those children, and used a questionnaire to screen them for autism spectrum disorders. When 189 of the children turned 21 years old, 60 percent of those who screened positive for an autism spectrum disorder, and 24 percent of those who screened negative with the condition.  All in all, the rate of autism spectrum disorders among the study participants with low birth weights was five times higher than the general. Autism spectrum disorder makes people have difficulty communicating, difficulty interacting in social situations, and restrictive or repetitive interests, said study co-author Jennifer Pinto-Martin, a researcher in the University. Those with mild autism spectrum disorders, \"may only want to talk about one subject,\" Pinto-Martin said. \"They\'re perfectly functional. They can go to college. They can hold a job.\" Premature babies are often born with low birth weights, though full-term babies can also have the condition. The research suggests a need not only for better prenatal care to reduce the number of premature babies, but also a need for early diagnosis and intervention for people with autism.