background Autism spectrum disorders (asd) occur in 0,6% of the general population. On the basis of research in the 70s, 80s and 90s many experts came to the conclusion that asd were in fact genetically determined and were linked only slightly to environmental factors. Recent research, however, indicates that environmental factors really do play an important role.
aim To describe and identify the main trends in current research into the causes of asd.
method The literature was studied with the help of Medline, Cochrane, Web of Science and ScienceDirect.
results Recent studies indicate that there is an underlying genetic cause in 35 to 60% of the cases of asd. Environmental factors play a greater role than previously thought and trigger the development of asd in people with a genetic vulnerability to asd. Not only is there evidence of risk factors for asd, but there is also evidence that certain factors protect against asd, for instance the use of folic acid before and during pregnancy.
conclusion asd are probably related to a combination of gene mutations and environmental factors and to the interactions between the two. Further research is needed into the genetic and environmental causes of asd.