It had mostly long been presumed that there is a common cause at the genetic, cognitive, and neural levels for the social and non-social components of ASD's symptoms, described as a triad in the classic autism criteria. However, there is increasing suspicion that autism is instead a complex disorder whose core aspects have distinct causes that often co-occur. While it is unlikely that a single cause for ASD exists, many risk factors identified in the research literature may contribute to ASD development. These risk factors include genetics, prenatal and perinatal factors (meaning factors during pregnancy or very early infancy), neuroanatomical abnormalities, and environmental factors. It is possible to identify general factors, but much more difficult to pinpoint specific factors. Given the current state of knowledge, prediction can only be of a global nature and therefore requires the use of general markers.

Biological subgroups
Research into causes has been hampered by the inability to identify biologically meaningful subgroups within the autistic population and by the traditional boundaries between the disciplines of psychiatry, psychology, neurology and pediatrics. Newer technologies such as fMRI and diffusion tensor imaging can help identify biologically relevant phenotypes (observable traits) that can be viewed on brain scans, to help further neurogenetic studies of autism; one example is lowered activity in the fusiform face area of the brain, which is associated with impaired perception of people versus objects. It has been proposed to classify autism using genetics as well as behavior.