The First Discovery of the Role of Viruses
In 1971, Stella Chess wrote an article, in which she first proposed that autism is a result of rubella infection in pregnancy. In her study, 243 children infected with congenital rubella virus were studied.
Out of these children, only 50 did not have any pathologies. 107 children, which is 44% had hard neurological pathologies, and 18 of them had autism. Other pathologies included: visual in 80 children, hearing in 177 children, soft neurological pathologies in 59 children, and cardiac in 85 children. Most children had more than one condition.
These findings led Chess to the following conclusion:
The common denominator in our sample is that all the children were at risk for prenatal invasion of the CNS by the rubella virus. It seems reasonable to speculate that the common component in our autistic children is brain damage.
This study showed that in children with autism congenital rubella virus is detected 200 times more often than in children without autism.
ABA-Therapy: the Beginning
During the 1970's, psychological approaches to corrective behavioral therapy were in development.
In 1977, Paul Margolies published a review article summarizing the findings of experiments based on the concept of rewarding those with good behavior, and punishing those with poor behavior.
These findings would be the foundations for ABA therapy, the basis of which was formulated in 1987.
Also in the 1970's, studies analyzing brains of those who were autistic gained popularity.
During this time it was observed that neocerebellar vermal lobules VI and VII were significantly smaller in comparison to healthy children, the cerebellum was asymmetric, and the number of Purkinje cells was reduced.
You can read more about brain alterations here
The First Genetic Study
In 1977, the famous twin study was published. The co-author of this study Michael Rutter, a person who contributed to autism research with dozens of studies.
It was shown that ASD has a genetic component. The pre-condition for the research was epidemiological finding that there is a 50-fold increase of autism risk in siblings of autistic children than in other children. In this study, 21 pairs of twins were studied.
Out of these 21 pairs, 11 were monozygotic (the same genes in both children) and 10 dizygotic (different genes), at least one child in twin pairs had to be autistic. The concordance for some kind of cognitive impairments in the second twin of monozygotic pair was 82%, while the concordance in dizygotic pair was only 10%.
These results pushed the new branch of autism research into the scientific community - genetic studies, about which you can read here