Autism and schizophrenia may be two sides of the same coin, suggests a review of genetic data associated with the conditions. The finding could help design complementary treatments for the two disorders.
Though autism was originally described as a form of schizophrenia a century ago, evidence for a link has remained equivocal. One theory puts the conditions at opposite ends of a developmental spectrum.
To investigate, Bernard Crespi, an evolutionary biologist at Simon Fraser University in Vancouver, Canada, and colleagues gathered data on all known genetic variants associated with each condition, then looked for patterns of co-occurrence.
The researchers found four regions in the genome which dramatically affect the risk of autism or schizophrenia. Called "copy-number variants", these are stretches of DNA with seemingly accidental duplications or deletions. Crespi's team found that the presence of a particular variant – a duplication, say – was often associated with autism while the opposite variation – a deletion of the genetic material – was linked to schizophrenia.
The results fit with other evidence that autism may be caused by overdevelopment of specific brain regions and schizophrenia by underdevelopment, says Crespi.
If they are indeed opposites, work on one disorder may inform work on its counterpart, he says.
Journal reference: Proceedings of the National Academy of Sciences, DOI: 10.1073/pnas.0906080106