Scientists with the Mailman School of Public Health Center for Infection and Immunity at Columbia University College of Physicians and Surgeons claim that there is no link between the measles-mumps-rubella vaccine (MMR) and autism development, but their findings are the result of an analysis of only 25 children with autism.

Dr. W. Ian Lipkin, director of the Mailman School of Public Health Center for Infection and Immunity, said in a statement that researchers failed to find any evidence that gastrointestinal pathology consistently preceded autism, or that the MMR consistently precedes either autism or gastrointestinal pathology.

The experts actually tried to replicate a controversial study which was the only somewhat credible evidence that there might be a link between MMR and autism. The original study, which was published in 1998, linked the presence of measles RNA in the gastrointestinal tract of those children who had autism and gastrointestinal problems. That study was however since discredited, and now it was apparently buried by the new research.

The researchers at the Columbia University Mailman School of Public Health’s Center for Infection and Immunity, who collaborated with scientists from the Massachusetts General Hospital, Trinity College Dublin, and the U.S. CDC, analyzed bowel tissues from 25 children, all with both autism and gastrointestinal problems, in addition to other 13 kids with only gastrointestinal problems. The analysis was performed at three different laboratories.

Some allege that a combination vaccine for measles, mumps and rubella, or MMR, plus a mercury-containing preservative called thimesoral can cause autism. This theory is not accepted by many medical experts, including the Institute of Medicine, the U.S. Centers for Disease Control and Prevention and the American Academy of Pediatrics.  Over the past years, many pharmaceutical companies have removed thimesoral from their vaccines intended for children, except flu vaccines, but its removal has appeared to have no effect on autism rates.

It appears that autism is caused by the deletion of some genes and turning off of other genes, which cause disruptions in the brain's ability to form new connections in response to experience. This means that autism may fundamentally amount to molecular defects in learning.

It is still unclear what the cause for autism is, but a combined cause with a large genetic component is suspected. People affected by the disorder are characterized by social impairments and often lack the intuition about others that many people take for granted. Autism Spectrum Disorders are associated with periods of severe tantrums and one third of autistic children also have displayed aggression, especially when the disorder is associated with mental retardation (as it often happens).