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Researchers say regression in autism common, variable, maybe universal

NIH scientific workshop focuses on understanding the brain changes behind regression, or loss of skills, in young children with autism
February 22, 2016


On Friday, Feb. 19, scientists at an international workshop on regression in autism made clear that researchers no longer doubt parent reports of the heartbreaking loss of language and social skills seen in some young children with the disorder.

To the contrary, the consensus at the workshop was that regression may represent a near-universal aspect of autism that can affect far more developmental skills than just speech. New research, for example, suggests that regression in babies can take the form of subtle losses in motor skills and attention to social cues. Parents and doctors are less likely to notice these early signs of autistic regression than they are the loss of language and sociability seen when regression takes place in toddlers who’ve already begun talking.

“We understand now that regression is common, it starts early, and it can affect many different developmental skills,” comments Paul Wang, Autism Speaks’ head of medical research. Dr. Wang was part of the workshop’s online audience of researchers, journalists, members of the autism community and the general public.

During the workshop, which took place at the National Institute of Mental Health (NIMH), in Bethesda, Maryland, more than a dozen leading autism researchers presented findings from recent and current studies on regression.

The presenters included several members of the Baby Siblings Research Consortium, which is supported by Autism Speaks. Some of the strongest scientific evidence of regression has come through research on the younger siblings, or “baby sibs,” of children diagnosed with autism. Because autism tends to run in families, around one in four baby sibs will develop autism by age 3. Another one in five will develop some autism symptoms, though not to the degree that brings a diagnosis of autism. Studying how these babies develop is deepening understanding of how autism unfolds and promises to guide improved methods for early detection and intervention.

The three sessions of the NIMH workshop included new findings on autistic regression in babies and toddlers, presentations on how animal and brain tissue studies can deepen understanding of the brain biology behind regression, and a discussion on how new biological insights into regression can improve early diagnosis and intervention.

View the archived webcast of the entire workshop, here.

A synopsis of the morning session on new insights into the nature of regression follows below.

Annette Karmiloff-Smith, of the University of London, discussed evidence that the loss of skills seen in autistic regression may stem from too much of the otherwise normal pruning away of excess brain connections during early brain development.

This included discussion of skill regression in typically developing infants. For example, she noted that between ages 3 to 6 months, typically developing infants can recognize parts of speech from many languages. If a baby isn’t exposed to multiple languages by 9 months of age, this ability disappears along with the brain connections associated with it. At the same time, the brain strengthens connections associated with the one language that will become the child’s “native” tongue.

“Different parts of the brain are pruned at different periods in development,” Karmiloff-Smith explained. “Our hypothesis is that in autism spectrum disorder, there’s an imbalance between the strengthening and pruning away of brain connections. It may be that the threshold is very high for pruning. So that [the brain] prunes away not just the weak connections but also the connections that should be strengthened.”

While loss of language tends to be what parents notice in toddlers, Karmiloff-Smith described recent studies with baby siblings that documented earlier, more subtle signs of regression. These included loss of early fine motor skills and a decline in a baby’s tendency to focus on social cues such as eyes and friendly voices.

Karmiloff-Smith emphasized that regression may be much more common than once thought based solely on loss of spoken language. If a child hasn’t yet developed speech when the excess pruning of brain connections takes place, she explained, then the associated “regression” in communication skills may not be obvious to parents, doctors and other caregivers.

In closing, Karmiloff-Smith called for more research with baby siblings to confirm whether “overaggressive pruning” of brain connections is, in fact, behind regression in autism.

Kasia Chawarska, a baby sibs researcher with the Yale Child Study Center, noted that Leo Kanner, the “grandfather” of autism research, was noting regression that involved language loss 60 years ago. Kanner divided autism into two types: innate, or present since birth, and regressive, or starting around 18 months of age. This led to the belief that children who lost language at 18 months were developing typically before regression, Chawarska noted.

“Since then however, research has shown that developmental challenges are occurring much earlier, during what was considered the pre-regression period,” she said. If one looks just at loss of language in toddlers, then regression is evident in about 15 percent of children with autism, she noted. But if one looks broadly at other areas of development and at younger children who are not yet speaking, then regression becomes evident in at least 80 percent of children who have autism or will go on to be diagnosed with it.

Chawarska described recent research using technology to detect subtle signs of regression not easily seen through ordinary observation. “If we track attention down to the millisecond using eye tracking, we see decreases in [attention to social cues] much earlier,” she said.

She also described baby sibs research that identified a “recovery group” of young children who begin losing skills and developing symptoms of autism in the first year of life and then begin regaining skills and losing autism symptoms around 18 months. “What is happening here?” she asked. (See graph with blue lines in the slide below.)

“Regression is not an event, it’s a process,” she emphasized. “Often it’s a very protracted process that extends over months. But trying to categorize those who have regression from those who don’t can be like drawing a line in the sand.” We might understand regression better, she proposed, by seeing it as a dimension of autism rather than a type of autism – with some children experiencing a lot of regression and some much less.

She urged broader research that includes more-subtle types of regression than just language loss, as well as research on how and why some young children recover from what looks like regression.

Jason Wolff, of the University of Minnesota discussed insights from the Infant Brain Imaging Study (IBIS), which Autism Speaks also helps support.

He noted brain imaging research by his team and others that associates regressive autism with overgrowth of the brain in the first year of life. Often, this period of overgrowth is followed by a marked slowing of growth so that the brain ends up smaller than average by age 3.

Using noninvasive brain imaging, Wolff’s team found an overabundance of brain connections at 1 year in baby sibs who went on to be diagnosed with autism. But by 2 years of age, these children tended to have fewer brain connections than is typical for their age.

Wolff noted similar findings from at least three other independent research groups. “But we just don’t know what this means,” he said. “We can learn only so much through neuroimaging.”

“A lot of pruning takes place in the first year of life,” he notes. “Is this setting the stage for autism, for loss of skills?” he asked. One thing is certain, he added: “This story won’t be the same for every child with autism.”

View the archived webcast these presentations, along with the workshop’s other scientific sessions, here.

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