Review
Getting answers from babies about autism

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Because autism is rarely diagnosed before two years of age, little is known about its early symptoms and causes. In order to determine the earliest manifestations of the condition, recent interest has focused on infants at genetic risk for autism. Current evidence indicates that overt behavioural symptoms emerge around the end of the first year. However, studies using laboratory brain function measures have reported differences in groups of infants at-risk compared with low-risk controls during their first year. Some infants displaying such early differences, however, do not subsequently receive a diagnosis. As the search for early markers continues, infants at-risk present a persuasive model for gene by environment interactions leading to variable developmental pathways.

Section snippets

What can babies tell us about autism?

Autism Spectrum Disorders (ASD) affect 1 in 100 to150 children [1]. The annual societal cost of ASD in the UK exceeds £27 billion [2]. Our current knowledge of the early neural, behavioural and cognitive profile is very poor, and little is known about the underlying causes of ASD or the process through which symptoms emerge. Because a confirmed diagnosis of ASD can only be made from around two or three years of age (Box 1) researchers, until recently, have relied on limited retrospective data

Early signs

Despite recent advances in our understanding of the genetic and neurobiological basis of ASD, the condition is currently diagnosed on the basis of behavioural characteristics that can take qualitatively different forms in infancy. Tools currently used for screening and diagnosis, relating to the three areas affected in ASD (social abilities, communication and repetitive behaviours), have been validated for children of 18 months and older but not for younger infants (Box 1). Thus, most

Different pathways towards an ASD diagnosis?

The lack of uniformity in the nature and timing of early markers among infants, and their probabilistic nature in terms of predicting diagnosis, has generated interest in the notion that there are multiple pathways to ASD. Traditionally, two subgroups have been hypothesised based on their trajectory of symptoms [24]. The first trajectory characterises infants whose symptoms appear early in development and become clearer with age. The second trajectory involves typical initial stages of

Getting beneath behaviour

Whereas the majority of infant siblings studies to date have searched for atypicalities in social behaviour, a few laboratories have recently used methods from developmental cognitive neuroscience with this risk group. The motivation is that more direct measurements of brain function or cognition might reveal indicators of atypical development before these become evident in the overt social behaviour of the infant. Because work with such methods is relatively new, there is little current data

Babies at-risk for ASD and gene–environment interaction

Researchers in areas of genetics and developmental psychopathology have invoked gene by environment interaction to help explain why an early genetic or environmental perturbation affects some individuals and not others [39]. In Figure 3 we illustrate some of the underlying assumptions about how genetic or environmental risk factors operating within the infancy period give rise to later behavioural outcomes. Although our focus here are those factors leading to ASD, it is likely that similar

Concluding remarks

Attempting to understand the ways in which genes, brains and the environment operate and interact is an enormous challenge. Owing to the fruitful integration of theories from different disciplines, innovative methodologies, and a successful alliance of scientists, babies and their families, we are at the cusp of very exciting discoveries. Studies of infant siblings of children affected by ASD are beginning to reveal how genetic risk for developing the condition takes them through diverging

Acknowledgements

We wish to sincerely thank all the families taking part in the British Autism Study of Infant Siblings (BASIS, www.basisnetwork.org). We wish to specifically thank those families and researchers who have given consent to the use of their photographs. BASIS is approved by the London Multicentre Research Ethics Committee, UK. Although the specific views expressed are our own, we are grateful to our collaborators Patrick Bolton, Tony Charman, Andrew Pickles, Atsushi Senju, Teodora Gliga, Janice

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