Girls may show different symptoms
Girls with mild autism are less likely to be identified and diagnosed than boys, a study suggests.
Researchers examined 493 boys and 100 girls with autistic spectrum disorders.
They found the girls showed different symptoms, and fewer signs of symptoms traditionally associated with autism, such as repetitive behaviour.
The researchers, who presented their work to a Royal College of Psychiatrists meeting, said this might mean cases among girls are missed.
Autism is thought to affect four times as many boys as girls - but the latest study suggests this might not be the case.
Most of the children featured in the study had been seen at the Social and Communication Disorders Clinic at Great Ormond Street Hospital in London. Additional cases came from Sunderland and Finland.
All the children were classified as "high-functioning". They did not have classic autism, but did have difficulties with socialising and communication.
The researchers, who have yet to publish their research, found that the girls were more likely to have obsessional interests centred around people and relationships.
However, these interests were more likely to be acceptable to their parents, and therefore tended not to be reported to doctors.
In addition, these types of obsessions were less likely to be discovered using standard diagnostic questionnaires.
The investigators said more research was needed to analyse how autism spectrum conditions manifest differently in the sexes.
Professor Simon Baron-Cohen, an autism expert at the University of Cambridge, agreed.
He said: "This is an important clinical issue and there are too few studies addressing it.
"We shouldn't assume autism or Asperger syndrome will look the same in both sexes.
"There may be many factors leading to these conditions either being underdiagnosed or misdiagnosed in females, or leading females to require a diagnosis less often."
Judith Gould, of the National Autistic Society, said: "We hear from many women who have been diagnosed later in life.
"The way autism is presented in women can be very complex and so can be missed.
"It might be that due to misconceptions and stereotypes, many girls and women with autism are never referred for diagnosis, and so are missing from statistics.
"This may mean that many women who are undiagnosed are not receiving support, which can have a profound effect on them and their families."
Ms Gould said it was also possible that girls were better at masking difficulties in order to fit in with society.
"Characteristics such as shyness and oversensitivity, common to people affected by autism, are sometimes deemed to be typically female traits.
"However if a boy were to display such characteristics, concerns may be raised."