New Insights on Autism….

Contemporary diagnostic criteria for autism have not changed much from the original descriptions offered by Leo Kanner in 1943 [1]. The three core features, which all individuals with autism must exhibit in order to be formally diagnosed, are impairments in social interaction, impairments in communication, and restricted and repetitive interests and activities. Most research seeking to discover causal factors in autism assumes that these three features must have a single source. Francesca Happé, Angelica Ronald, and Robert Plomin challenge that notion in an article published today in Nature Neuroscience [2].

In a somewhat unusual approach to assessing core autism traits, the authors note that these traits can be measured in the general, non-clinical population. For example, a child could be rated on how easily he or she joins a group of children to play, maintains a two-way conversation, or plays in rigid, repetitive ways.

Based on their assessment of 3000 non-clinical twin pairs between the ages of 7 and 9 years, Happé et al. argue that while the three core features do appear to overlap in the general population, their relationships are not as robust as we might otherwise assume. For example, social and communication difficulties were only modestly related (r=0.2 to 0.4). 

The authors found many children who had difficulties in a single area (social skills without language impairment or ritualistic play) of the same severity normally seen in autism. Others have previously pointed out that family members often show sub-clinical levels of impairment in one or more of the three core areas. These findings support the notion of some independence among the three core features.

In addition, the authors propose that explanations suggesting that one feature explains the development of others (i.e. social difficulties lead to communication problems) fail to adequately predict the development of ritualistic play. Nor do “Theory of Mind” explanations account for language difficulties or ritualistic play.

Based on what they refer to as the “fractionation” of autism’s core features, the authors suggest that future research concentrate on only one aspect of the condition. Instead of searching for “autism genes,” perhaps a more fruitful approach would be to look for genes related to social functioning or language functioning. Likewise, instead of attempting to design treatment plans based on the combination of features, more specific treatments could be aimed at each feature individually.

This is an interesting and potentially valuable perspective for understanding autism. However, this approach leaves us without an explanation for why the three features appear together in the same person so frequently. Is this an alignment of the planets? Bad luck? Perhaps we can still identify factors that begin the cascade of events leading to all three features.

[1] Kanner, L. Autistic disturbances of affective contact. Nervous Child 2, 217–250 (1943).

[2] Happé, F., Ronald, A., & Plomin, R. (2006). Time to give up on a single explanation for autism. Nature Neuroscience, 9, 1218-1220.