Researchers say they have discovered a link between childhood autism and mental illness in parents; they suggest that the parents of autistic children are twice as likely to have had a psychiatric illness.
The researchers at the the University of North Carolina at Chapel Hill in the States, examined the records of more than 30,000 children and found that rates of autism rose substantially if parents had suffered schizophrenia, depression or a range of other personality and psychiatric disorders.
They say a child's risk of autism is 70% greater if one parent was diagnosed with a mental illness, and twice as high as average if both parents had psychiatric disorders.
The suggestion is that autism and psychiatric problems possibly have a common cause and a genetic link.
The researchers, led by Julie Daniels examined the medical records of 1,237 Swedish children born between 1977 and 2003 who were diagnosed with autism before the age of 10.
The records were linked to their parents' medical histories, which included details of any mental disorders they had been treated for and then compared to the medical records of a further 30,925 healthy children.
Dr. Daniels says their research showed that mothers and fathers diagnosed with schizophrenia were about twice as likely to have a child diagnosed with autism and higher rates of depression and personality disorders were seen amongst mothers, but not fathers of autistic children.
The strongest association between a child's autism and a parent's mental illness in the parent was with schizophrenia.
The finding supports previous research which also indicated a genetic basis for autism where studies on twins have shown that if an identical twin has autism, the chances of the other twin also being autistic are extremely high.
Autism appears in about 1% of children and boys are four times more likely to develop it than girls.
Earlier this year, the largest study on the issue dismissed any link between the MMR triple vaccine and autism.
The latest research will help doctors to distinguish between the different types of behavioural disorder which come under the label of autism.
Dr. Daniels who is an assistant professor in the UNC School of Public Health's epidemiology and maternal and child health departments, says autism includes a wide spectrum of disorders that are probably caused by different things and the more groups of individuals with the classification of autism can be refined, the better equipped scientists will be to look for causes and treatments.
The research is published in the journal Pediatrics.