A New Scientist article 29 June 2010 by Jim Giles states:-

We still do not know what causes autism.“

Desperate measures: The lure of an autism cure

That is not correct. Here we set out four ways autistic conditions are caused.

The first known cause of autism was rubella virus. This has been known since the 1960s. Live rubella virus is one of the three live viruses in the MMR vaccine.

congenital rubella can cause autism”

The Pediatrician’s Role in the Diagnosis and Management of Autistic Spectrum Disorder in Children – PEDIATRICS Vol. 107 No. 5 May 2001

Autistic conditions can result from acute disseminated encephalomyelitis (ADEM) following MMR vaccination as held by the US Federal Court in the case of Bailey Banks.  In his conclusion, US Federal Court Special Master Abell ruled that Petitioners had proven that the MMR had directly caused a brain inflammation illness called acute disseminated encephalomyelitis (ADEM) which, in turn, had caused the autism spectrum disorder PDD-NOS in the child:

The Court found that Bailey’s ADEM was both caused-in-fact and proximately caused by his vaccination. It is well-understood that the vaccination at issue can cause ADEM, and the Court found, based upon a full reading and hearing of the pertinent facts in this case, that it did actually cause the ADEM. Furthermore, Bailey’s ADEM was severe enough to cause lasting, residual damage, and retarded his developmental progress, which fits under the generalized heading of Pervasive Developmental Delay, or PDD [an autism spectrum disorder]. The Court found that Bailey would not have suffered this delay but for the administration of the MMR vaccine, and that this chain of causation was… a proximate sequence of cause and effect leading inexorably from vaccination to Pervasive Developmental Delay.

[Banks v. HHS (Case 02-0738V, 2007 U.S. Claims LEXIS 254, July 20, 2007)].

Autistic conditions can result from encephalopathy following vaccination.  The US Health Resources and Services Administration (HRSA) confirmed to CBS News that of 1322 cases of vaccine injury compensation settled out of court by the US Government in secret settlements:-

We have compensated cases in which children exhibited an encephalopathy, or general brain disease. Encephalopathy may be accompanied by a medical progression of an array of symptoms including autistic behavior, autism, or seizures.”

CBS News Exclusive: Leading Dr.: Vaccines-Autism Worth Study Former Head Of NIH Says Government Too Quick To Dismiss Possible Link – WASHINGTON, May 12, 2008

Vaccine Case: An Exception Or A Precedent? – First Family To Have Autism-Related Case “Conceded” Is Just One Of Thousands – CBS News By Sharyl Attkisson WASHINGTON, March 6, 2008

Measles and mumps are two of the three live viruses in the MMR vaccine. Exposure to live measles or mumps viruses can cause encephalitis:-

measles and mumps can cause significant disability, including encephalitis“

The Pediatrician’s Role in the Diagnosis and Management of Autistic Spectrum Disorder in Children – PEDIATRICS Vol. 107 No. 5 May 2001

So there is direct evidence that live measles, mumps or rubella viruses separately can cause encephalitis leading to autism.

More troubling is that this has been known for a long time.  So the risks of giving very young children a vaccine containing three live viruses all at once were known. These two World Health Organisation papers published nearly 40 years ago set out the hazards:

Virus-associated immunopathology : animal models and implications for human disease”:

1. Effects of viruses on the immune system, immune-complex diseases, and antibody-mediated immunologic injury Bulletin of The World Health Organisation. 1972; 47(2): 257-264.

2. Cell-mediated immunity, autoimmune diseases, genetics, and implications for clinical research Bulletin of the World Health Organisation. 1972; 47(2): 265-274.

People who are pre-disposed to have a mitochondrial dysfunction can develop autistic conditions following vaccination.  The current President of Merck’s Vaccines Division, Julie Gerberding confirmed to CBS News when she was Director of the US Centres for Disease Control that:

….. if you’re predisposed with the mitochondrial disorder, it can certainly set off some damage. Some of the symptoms can be symptoms that have characteristics of autism.“

HOUSE CALL WITH DR. SANJAY GUPTA – Unraveling the Mystery of Autism; Talking With the CDC Director; Stories of Children with Autism; Aging with Autism – Aired March 29, 2008 – 08:30   ET

Mitochondrial dysfunction is claimed to be “rare” but is not.  It can apply to a minimum of 20% of cases.

And this was said when Gerberding was then head of the US Centres for Disease Control – budget US$11 billion.  It followed from  award winning author and journalist David Kirby breaking the story of the Hannah Poling case, secretly settled by the US Government.  It was after this story broke that it started to be acknowledged that autism has an “environmental” cause and is not solely an “internal” condition [ie not determined solely by genetics]: AUTISM – US Court Decisions and Other Recent Developments – It’s Not Just MMR

[Gerberding went from the US agency charged with promoting vaccines [CDC] directly to become vaccine maker Merck’s Director of Vaccines Division: Dr. Julie Gerberding Named President of Merck Vaccines – 21 Dec 2009 – Merck & Co., Inc.

And what does not cause autism?

Autism is not “caused” by “genes”

Dr Francis S. Collins, M.D., Ph.D. the 16th and current Director of the US$30.5 billion budget National Institutes of Health [nominated by President Obama: NIH News Release 17th August 2009 ] stated in evidence to US House of Representatives Committee May 2006 when Director of the US National Human Genome Research Institute:

“Recent increases in chronic diseases like diabetes, childhood asthma, obesity or autism cannot be due to major shifts in the human gene pool as those changes take much more time to occur. They must be due to changes in the environment, including diet and physical activity, which may produce disease in genetically predisposed persons.“

Francis S. Collins, M.D., Ph.D. evidence to US House of Representatives Committee May 2006

Collins controls the US $30.5 billion annual medical research budget and is a leading medical doctor and geneticist who led the Human Genome Project.

Autistic conditions affect 1 in 100 US children.  They affect 1 in 64 British children [1 in 40 are boys] according to a Cambridge University study.

ESTIMATING AUTISM SPECTRUM PREVALENCE IN THE POPULATION: A SCHOOL BASED STUDY FROM THE UK

Conclusions: The prevalence estimate of known cases of ASC, using different methods of ascertainment converges around 1%. The ratio of known to unknown cases means that for every three known cases there are another two unknown cases. This has implications for planning diagnostic, social and health services.”

It is estimated to cost the UK £28 billion per annum [roughly US$42 billion]: ["Economic Consequences of Autism in the UK" - London School of Economics - Study by team led by Professor Martin Knapp [Executive Summary]