The issue of a possible genetic link between autism and schizophrenia has been the subject of recent studies. Two recent studies found certain gene mutations that make some individuals or their children more prone to the development of schizophrenia or autism. The findings support the argument for possible genetic causes of autism. It is also reminiscent of the long history of confusion between childhood schizophrenia and autism.
Historical Associations Between Autism and Schizophrenia
In the early history of autism, many doctors misdiagnosed autistic patients as schizophrenic. The two neurological disorders are separate medical conditions but some of the symptoms of autism are similar to schizophrenia. To many people, this association is surprising because autism usually manifests in early childhood and schizophrenia often presents in early adulthood. However, early on-set schizophrenia, or childhood schizophrenia, though rare, sometimes occurs in 1 in 40,000 children. According to the Yale Child Study Center, children with autism were often diagnosed as having a form of childhood schizophrenia until the late 1970s. Childhood schizophrenia and autism are now considered two separate neurological conditions.
The Genetic Link Between Autism and Schizophrenia
For years, many autism experts have thought that autism and schizophrenia shared similarities and a possible common origin. Scientists have searched for autism genes and schizophrenia genes. Whole genome scanning of DNA has helped this research effort. Recent studies found evidence of common gene mutations and irregularities in the same areas of human genome in the two disorders. It was also discovered that many people with autism and schizophrenia also have unusual duplications or deletions in their DNA.
Common Gene Mutations
In 2008, Autism and schizophrenia expert Judith Rapoport of the National Institute of Mental Health and her research team found that people with autism and schizophrenia had a tendency for a certain pattern of gene clustering that was rare in majority of the population. Rapoport also discovered that many people with schizophrenia and autism had unusual brain growth before the age of three.
A 2009 John Hopkins study discovered more evidence that autism and schizophrenia have common genetic fingerprints aka DNA fingerprint or series of DNA base pairs when manipulating genes to study the susceptibility to schizophrenia. While scientists did not claim that the discovered genes cause autism or schizophrenia, they believe the identification of the genetic fingerprints can help further research into possible causes and treatments for both disorders.
Common Region of Human Genome Abnormalities
In 2009, researchers from Simon Fraser University in Vancouver (Canada) looked deeper into the possible gene connection between autism and schizophrenia. The study found that autism and schizophrenia have abnormalities in same areas of the human genome. The surprising discovery is that the two disorders, while sharing a similar region of impairment in the human genome, are genetic opposites in the presentation of the abnormality. People with typical brain development have two copies of each gene. Researchers discovered that many people with autism have only one copy of certain genes, while many people with schizophrenia have duplicate copies of certain genes.
Schizophrenic Parents and Autistic Children
A 2008 University of North Carolina at Chapel Hill study discovered that parents with a preexisting mental illness, such as schizophrenia, are more likely to have children with autism. Researchers examined the medical records of 30,000 children and 1,237 Swedish children who were diagnosed with autism before the age of 10. The researchers also reviewed the parents' medical records. The study found that children had a 70 percent greater risk of developing autism than the families with no history of mental illness. The risk for autism was twice the average if both parents had mental illnesses. Schizophrenia was the psychiatric disorder that had the highest incidence of autistic children, suggesting a genetic link.
People with Autism Prone to Schizophrenia
A number of people with autism also have another medical condition, a phenomena known as comorbidity. Many experts believe the reason for the comorbidity of autism and schizophrenia must be a common genetic link or cause. A 1991 Yale Child Study Center study determined that the occurrence of comorbidity of autism and schizophrenia is not any higher than the general occurrence of schizophrenia alone. However, a 2006 study published in the Journal of Autism and Developmental Disorders argues that the occurrence of autism with psychiatric disorders, such as schizophrenia, is high.
Impact on Autism Genetic Argument
Since the cause of autism is unknown, scientists are still searching for answers. Autism experts continue to argue for possible causes ranging from genetic to environmental toxins. There are studies to support a number of different possible autism causes that warrant more research. However, there is not enough scientific evidence to support one autism cause at this time. This also makes it possible that there may be multiple causes of autism, especially since autism presents in many different forms and levels of impairments. The fact that a large number of studies, such as the autism and schizophrenia gene studies, suggest genetic connections to autism are among the many possible autism causes.
The studies that support the idea of a genetic link between autism and schizophrenia are important because they have provided more insight into possible autism causes. As research continues, these study findings can potentially lead to more effective autism treatments.