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2001 > September
Family traits provide clues to genetics of autism
It was widely believed in the 1950s and 1960s that autism was caused by “refrigerator moms” who failed to provide adequate emotional nurturing. Subsequent research—including a 1977 groundbreaking study of autistic twins co-authored by Dr. Susan Folstein, professor of psychiatry—replaced the bad parenting theory with evidence that autism has complex genetic roots.
Today, some autism investigators, including Folstein, once again are examining certain traits of autistic children’s parents and siblings. Armed with new genetic tools and data, they are seeking genetic links that could help pinpoint the genes and, eventually, molecular mechanisms involved in specific aspects of autism.
Autism was identified as a distinct disorder by Leo Kanner in 1943 in the United States and Hans Asperger in 1944 in Germany. “The influence of psychoanalysis as an explanation for everything was overwhelming in the late ’40s, ’50s and ’60s,” Folstein says in explaining why the introverted nature of many of the parents of autistic children was easily seen as the cause of the disorder. The “bad parenting” explanation for autism was weak for a variety of reasons, including the failure of psychoanalysis to help and the development of epilepsy in some cases, which pointed toward a biological cause.
Studies of twins provided further support. It is estimated that autism affects about one in every 1,000 children. However, there’s a 6 to 8 percent chance the sibling of an autistic child will be autistic. And among identical male twins, the chance that both are autistic is 50 percent.
The “normal” identical twin, however, is likely to have some autistic behaviors, according to Folstein. She first made this observation in the 1970s, when she was tracking down autistic twins in England. “I noticed as I went around to see the families, the parents were sometimes peculiar—exceedingly orderly and often showing great difficulty expressing themselves. I also noted that in the [identical] twins, where only one was autistic, the other often had some of the traits that comprise autism, such as a social phobia or verbal learning disabilities.”
Later, back in the United States, Folstein conducted a large study involving 75 families with autistic children. She found that 30 percent of the parents had at least one autistic-type trait, including rigidity about the way things should be done; social reticence, including strong dislike of small talk and large groups; or language structure difficulty, such as late onset of speech or problems writing narratives.
Folstein and a collaborative group she helped organize six years ago are using the family studies as a base for genetic linkage studies. That group, including researchers from Vanderbilt, the University of Iowa and the University of North Carolina, published its first linkage study, implicating regions of chromosomes 7 and 13 as possibly being involved in autism (American Journal of Medical Genetics/Neuropsychiatric Genetics, 88:609-615, 1999). In follow-up research, they have found that genes on these two chromosomes are related to one characteristic of autism—delayed onset of speech.