Different studies resulted in different numbers of the frequency of autism spectrum disorders. One study stated ten cases of classical autism, 2.5 cases of Asperger's syndrome and 15 cases of mild autism (PDD-NOS) in 10,000 people - tendency: increasing. Other sources speak about 60 autism spectrum disorder cases in 10,000 people. However, the number of autism cases is not equal in men and in women. Here, the results of studies vary highly. Researchers in general say that 3-4 men are diagnosed for every woman that is diagnosed. This ratio decreases for severe cases to 1:1. It increases for high-functioning cases and in Asperger's syndrome reaches a ratio of 8:1. Recently, the awareness has increased that this ratio may be so high because studies are simply missing female autistic people. This could be because tests for autism typically focus on male autism traits. Another possible explanation is that autistic females may be better at adapting to social expectations and hiding their social problems. Studies have suggested that the brains of autistic females may rather be like neurotypical men’s (non-autistic men) brains of the same age. These could be reasons why it is not so easy to realise whether a woman is autistic - and therefore, why more men than women are diagnosed.