What causes autism? What we know, don’t know and suspect
For a considerable time scientists were searching for one clear brain difference that may be lead to autistic behaviours. However, this hope has yet to be fulfilled, with few studies identifying brain characteristics that are shared by different individuals diagnosed with autism.
This may be a further indication that autism has many different causes, but it may also be a reflection of the difficulties in studying the brain.
Currently, scientists use a variety of clever techniques to understand the structure and function of the brain, such as magnetic fields, X-rays and radioactive chemicals. As ingenious as these methods are, they are unable to provide a full measure of the tremendous complexity of how the brain operates.
It is also unlikely that autism affects just one area of the brain alone. The complex behaviours of individuals with autism, which include cognitive, language and sensory difficulties, make it difficult to pinpoint just one brain region that may be affected. Nevertheless, some promising leads have shown how different brain pathways may lead to autistic behaviours.
There is increasing evidence that differences in brain development may begin prenatally in some individuals with autism. Several studies of prenatal ultrasound measurements have found evidence for differences in the growth patterns of the brain in fetuses later diagnosed with autism. Newborns later diagnosed with autism are often also reported to have large heads at birth (“macrocephaly”).