Science Update February 11, 2013
Precursor Symptoms to Autism Detected in 6-Month-Old Infants
Early signs of autism can be detected in 6-month-old infants, suggested a National Institute of Mental Health (NIMH)–supported study published online this January in Biological Psychiatry.
Autism spectrum disorders (ASD) typically manifest before the age of 3 years and are associated with a range of difficulties in social interaction, communication, and repetitive behaviors. The diagnosis of ASD is on the rise: current estimates by the U.S. Centers for Disease Control and Prevention suggest that about 1 in 88 American children are currently on the autism spectrum—a 10-fold jump over the past 40 years. It’s unclear whether this apparent rise in prevalence represents a real increase due to environmental and genetic factors or is due to better awareness and improved detection.
Early detection of ASD leads to earlier intervention which in turn may lessen, or even eliminate, ASD symptoms for some children. Yet identifying the earliest signs of ASD has been challenging. Some ASD patients develop symptoms before their first birthday; in others, symptoms become apparent later in the second or even third year of life. Children with ASD can be reliably diagnosed by 2 years of age, but research suggests that some screening tests can be helpful at 18 months or even younger.
Studies involving younger siblings of children with ASD have made some inroads toward identifying early diagnostic markers. If one sibling has ASD, the other siblings have 35 times the average risk of developing the disorder. The risk is even higher in identical twins: if one has ASD, 9 out of 10 times the other twin also has it.
Katarzyna Chawarska, Ph.D., at Yale University School of Medicine, New Haven, and her research team followed a group of infants from 3 months to 3 years of age. The infants were assessed in their third year of life when some of them were found to have ASD. In the study reported in Biological Psychiatry, they tracked eye movements of 6-month-old infants—67 at high-risk for ASD because their siblings had the disorder, 50 at low-risk because no one had ASD in their family—as they watched a video of an actress playing with toys and making a sandwich. Periodically the actress would speak directly to the camera and try to engage the baby using greetings (“How are you, baby?”), compliments (“You are so cute!”), and comments (“Did you see it? It was so much fun!”). The video did not try to attract the children’s attention by including the usual “attention getters” such as music. Rather, the children were allowed to look spontaneously at whatever they decided was most important to them.
Source: Annie Shic
“At any given point in time, we are bombarded with an immense amount of information from multiple sources. In order not to be overwhelmed, we selectively attend to what we find most important,” explained Chawarska. “From the earliest moments of our life, what we find most important are other people. We wanted to see if infants who later developed ASD showed attentional biases towards people similar to those observed in typically developing babies.”
Results of the Study
Compared to the control groups, infants later diagnosed with ASD, showed a decreased ability to pay attention to the complex social scene. They also spent less time looking at the actress and her face, but they did not look longer at the toys present in the scene. These findings suggest that difficulties in attention to people might precede the excessive interest in objects often reported in older children with ASD.
The findings indicate that some of the first signs of ASD, such as limited visual attention to social scenes, can be detected very early in development, well before the emergence of diagnostic features. Although it may be too soon to push the age of diagnosis down to the first year of life, the study suggests an important direction for further research as well as a tremendous window of opportunity to intervene.
The identification of precursor symptoms as a means for early detection and intervention remains a key priority in numerous fields of mental health research. For instance, the NIMH-supported North American Prodrome Longitudinal Study (NAPLS) is looking at the earliest stages of psychotic illness in those who develop schizophrenia and affective psychotic disorder.
More research is needed to delve into the specific causes that lead to differences in attention to complex social stimuli at such an early developmental stage. The impact of multiple factors, such as the roles of processing load, eye contact, and child-directed speech, require further clarification. Further research is necessary to determine if these differences can be seen in even younger babies.
Chawarska K, Macari S, Shic F. Decreased Spontaneous Attention to Social Scenes in 6-Month-Old Infants Later Diagnosed with Autism Spectrum Disorders. Biological Psychiatry, published online January 10, 2013.
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