Girls who are autistic have more “masculine” brains.

The new study found clear differences between the anatomy of the brains of male and females who have autism.

Scientists believe woman who have autism show “neuroanatomical masculinisation”, meaning their brains have similar traits to those of healthy males.

The team from the University of Cambridge's Autism Research Centre said our understanding of the neurobiology of autism is male-biased because the condition is more prevalent in men so research has been focused on them.

Autism affects one per cent of the population.

Researchers are hoping a greater understanding of autism in both sexes will improve the chance of finding best treatments.

Professor Simon Baron-Cohen, senior author of the study, said: “This may implicate physiological mechanisms that drive sexual dimorphism, such as prenatal sex hormones and sex-linked genetic mechanisms”.

Dr Meng-Chuan Lai, who led the research, said: “This is one of the largest brain imaging studies of sex/gender differences yet conducted in autism. Females with autism have long been under-recognized and probably misunderstood.  The findings suggest that we should not blindly assume that everything found in males with autism applies to females.  This is an important example of the diversity within the spectrum".

The study, entitled “Biological sex affects the neurobiology of autism”,  was published in the journal “Brain” this week.

Autism is a developmental disorder that affects the way a person communicates and relates to the people around them.