• By Laura Whybra
  • Posted on Monday 21st October, 2013

Studying twins yields new insights into autism and anxiety

Scientists have observed since the 1940s that many autistic children experience distressing levels of anxiety. But an exploration of autism and anxiety among twins now shows that anxiety symptoms are often a problem for both siblings, even when one twin has no autistic traits.The research, led by Victoria Hallett of London’s Institute of Psychiatry, is a step towards improving the diagnosis and treatment of anxiety symptoms that can cause life-long distress among people with persistent, stereotyped behaviors and deficits in communication and social interaction that are diagnosed as autism spectrum disorders (ASDs). To conduct their study, they recruited 146 families from the longitudinal Twins Early Development Study (TEDS) where one or both twin children – aged 10 to 15 – had a suspected ASD. Both twins were interviewed using a standard diagnostic questionnaire for anxiety and depression, and parents’ perceptions of their children’s symptoms were also tested using the same instrument. The results were compared with those obtained from a control group of 80 TEDS families where neither twin had been placed near the autistic spectrum.Anxieties within familiesAs expected, the levels of parent-rated anxiety symptoms in children with ASDs were significantly higher than among the control families. But there was no significant difference when twins themselves reported their symptoms. While those with ASDs had scored themselves less anxious than on their parents ratings, the opposite was true of the twins in the control group.A suggested reason for this is that parents of children with ASD pay more attention to their children because of their complex needs and are more aware of their anxious behavior. By contrast, parents of other 10 to 15-year olds may be less aware of their anxieties as the children grow less dependent. Another striking finding was that ‘unaffected twins’ – the co-twins of ASD children who showed few or no autistic traits – also scored significantly higher than control children on parent ratings of generalized anxiety, social anxiety and panic symptoms. In addition, the researchers identified a group of co-twins who had not been diagnosed with ASDs, but displayed autistic-like traits classified as “Broader Autism Phenotype” (BAP). Based on parent reports, they showed heightened symptoms of anxiety at levels comparable to those with diagnosed ASDs.Genes or environment?One possible explanation for these findings is that children with ASD and their twins were exhibiting a shared genetic vulnerability to different forms of anxiety. However, previous studies have suggested that the association between autistic-like traits and internalizing traits like anxiety is more strongly driven by shared environmental factors than shared genetic influences.Having set foot down the road, the research team now propose to continue using twin modeling to pursue a future goal of unraveling causal influences. Progress may, however, depend on developing new accurate methods of identifying anxiety in children with ASD, who may not have the capacity to communicate this themselves.*********Reference:Hallett, V., Ronald, A., Colvert, E., Ames, C., Woodhouse, E., Lietz, S., Garnett, T., Gillan, N., Rijsdijk, F., Scahill, L., Bolton, P. & Happe, F. (2013). Exploring anxiety symptoms in a large-scale twin study of children with autism spectrum disorders, their co-twins and controls. Journal of Child Psychology and Psychiatry doi: 10.1111/jcpp.12068

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