Although they are not yet known, there are strong indications that the causes of autism spectrum disorders are biological. It is likely that autism is not caused by a single factor. The evidence includes the following observations.

• Autism is often accompanied by other neurological symptoms and associated with other learning difficulties.
• By adulthood, about one in three persons with autism will have had at least two epileptic seizures.
• Most autistic children show unusual responses to sensory stimuli of any kind and have what have been called movement differences.
• Brain autopsies have shown abnormalities in the frontal lobes, limbic system, brain stem and cerebellum.
• Some 30 to 50 per cent of autistic children have abnormally high levels of serotonin, the chemical that transmits signals in nerve cells.
• The higher incidence of autism in families points to a genetic aspect.
• There is evidence that at least one type of autism is an immune-system dysfunction, its onset triggered by viral infections, or by antibiotics and vaccines.
• Some autistic children are unable properly to digest certain foods, notably casein and gluten, so that toxins called opioids enter the bloodstream and reach the brain to cause havoc in many sensory and cognitive functions.

During the 1990s, there has been a major push to promote research into the causes of autism. Much of the impetus for this came from parents’ support and advocacy groups. In the United States, for example, the Cure Autism Now Foundation (CAN) was formed to promote and fund biomedical and genetic research into the causes of autism "because we believe that these children cannot wait any longer." Children with autism during the previous 40 years, whether diagnosed or not, are a lost generation because so little was done to promote understanding of their disorders and appropriate treatments that would improve their quality of life. CAN found that autism was getting only 5 per cent of the levels of research funding devoted to other health disorders.

In the United States and Britain, the 1990s have seen more commitment by governments and charitable foundations to funding research into autism. In the late 1990s, various research centres have been set up, often as consortia of teams at several universities. In 1997, the National Institutes of Health in the United States announced a five-year, 27-million-dollar international collaborative network of research centers on autism, especially its genetic aspects—involving 24 universities in 13 states and four foreign countries.

Research findings are already being published, in popular media as well as scientific journals. One example is the discovery of the first autism-susceptibility gene in May 1997 by a consortium of researchers in Chicago and San Diego. Another is the finding by researchers at the University of North Carolina at Chapel Hill (and several other participating universities) of evidence for possible "DNA hotspots for autism genes."

Information about current autism theories and research may be found at the following sites:

• The Cure Autism Now Foundation: www.canfoundation.org and www.canfoundation.org/newcansite/resources/sciencesites.html
  
  
• The Autistic Research Foundation (TARF) in the Boston area http://ladders.org/tarf/ARC.htm
  
  
• The Collaborative Linkage Study of Autism at the New England Medical Center and Tufts University. http://www.autismgeneticresearch.org
  
  
• The Autism Research Unit at the University of Sunderland (England)http://osiris.sunderland.ac.uk/autism/
  
  
• The Autism Research Center at the University of Cambridge www.psychiatry.cam.ac.uk/arc/about.html
  
  
• Autism - an Overview, a thorough survey of the theories and potential treatments of autism
  www.healing-arts.org/children/autism-overview.htm
  
  
• The Autism Autoimmunity Project www.gti.net/truegrit
  
  
• At Ontario’s McMaster University, Dr Szatmari’s Autism/PDD Research Team has two main projects, genetic research and a follow-up study of high-functioning autistic children
  www.fhs.mcmaster.ca/cscr/autism.htm

Research on autism is welcomed as one sign of increased awareness of very challenging disabilities, after decades of neglect. However, we may be concerned if the specialized genetic research is at the expense of study of approaches to treatments that could make a difference to people already affected by autism. Over-emphasis on genetic aspects may not take enough account of various causes that are needed to explain the distinct types of autism. Bernard Rimland comments on the current emphasis on genetic research in "Genetic, Autism and Priorities" at www.autism.com/ari/editorials/genetics.html

During the year 2000, the possible role of vaccines (especially the MMR or combined Measles, Mumps, Rubella dose given to children at 15-18 months) in triggering a form of autism became a very contentious issue.
We present a summary and review in: Vaccines as a Factor in Autism: Focus on the MMR Vaccine.