Autism affects male and female brains differently, a study of 120 brain scans has suggested, and more research is needed to understand how autism affects females, according to the researchers.
Autism affects about 1% of the population but is more prevalent in males so most research has focused on them. However, new research from the University of Cambridge, published in the journal Brain, suggests that the condition could be more prevalent in girls than currently estimated as it can be harder to diagnose.
Autism data mostly male-biased
Experts said females with the condition could be more stigmatised than males - and it could be harder for them to be diagnosed at all.
Researcher Dr Meng-Chuan Lai said: "What we have known about autism to date is mainly male-biased. This research shows that it is possible that the effect of autism manifests differently according to one's gender.
"Therefore we should not blindly assume that everything found for males or from male-predominant mixed samples will apply to females. There really needs to be more research and clinical attention toward females 'on the spectrum'."
Dr Lai, along with fellow scientists from the Autism Research Centre, used magnetic resonance imaging (MRI) to examine how autism affects the brain of males and females.
They found striking similarities between the structural anomalies found in the brains of females with autism and neurological characteristics known to be different between ‘healthy’ males and females in general.
The findings partially conform to the ‘extreme male brain’ theory of Cambridge neuroscientist Profossor Simon Baron-Cohen. Yet, in contrast to this theory, scans of the male brains in the study didn’t exhibit any discernible ‘extreme’ masculine characteristics.
Masking secondary problems
Carol Povey, director of The National Autistic Society's Centre for Autism, said: "[This study shows] girls can be more adaptive than boys and can develop strategies that often mask what we traditionally think of as the signs of autism. This ‘masking’ can lead to a great deal of stress, and many girls go on to develop secondary problems such as anxiety, eating disorders or depression.
"It's important that we build on this study and more research is conducted into the way autism manifests in girls and women, so that we can ensure that gender does not remain a barrier to diagnosis and getting the right support."
The Cambridge study was the largest sampling to date of high-functioning adults with autism using MRI. The researchers mapped structural differences among the brains of women and men who were diagnosed with autism and compared the scans with those of typically developing peers.
Previous studies have shown a strong sexual divide in brain function, such as cognition and memory. This so-called sexual dimorphism in brain structure suggests that females with autism differ from men in cognition, in genetic and hormonal biochemistry, and in early brain over-growth.
The researchers found the sharpest distinction when measuring the volume of white matter: for females diagnosed with autism, scans showed that areas associated most with autism closely mimicked a male pattern of white matter volume.
However, the sample only included high-functioning subjects with no other neurological disorders, so its results may not apply broadly.
To read the study in full visit http://brain.oxfordjournals.org/content/early/2013/08/08/brain.awt216.short?rss=1