Autism, Brain, and Environment

  • Richard Lathe
Jessica Kingsley: 2006. 288 pp. £15.99, $24.95 1843104385 | ISBN: 1-843-10438-5

Understanding Autism: From Basic Neuroscience to Treatment

Edited by:
  • Steven O. Moldin &
  • John L. R. Rubenstein
CRC Press: 2006. 526 pp. £92, $159.95 0849327326 | ISBN: 0-849-32732-6

Are we witnessing an autism epidemic? The current prevalence estimates for autism, and for the wider range of autism spectrum disorders (ASDs), are around ten times greater than estimates from studies in the 1980s and 90s. About 0.6% of the population is thought to have an ASD, diagnosed on the basis of qualitative impairments in social interaction and communication, with restricted and repetitive interests and activities.

The claim that cases of ASD are on the increase is the first step in Richard Lathe's argument in Autism, Brain, and Environment. Based on the apparent increase, Lathe argues for an environmental explanation for what he terms “new phase autism”. He recognizes the overwhelming evidence that autism is among the most heritable of psychiatric disorders, but argues for a two-hit mechanism, with genetic susceptibility and environmental factors combining to produce an ASD. His book is a clearly and accessibly written account of his proposal that environmental poisons, including heavy metals, interact with genetic vulnerability to cause damage to the limbic brain system and to physiological systems, including the gut and the immune system, resulting in autism.

This is a story that many readers will find plausible, and which Lathe supports with some good synthesis of established autism research. It is perhaps not surprising that he also cites less solid, unpublished research to support the hypothesis, nor that the limitations of such research, such as the lack of appropriate control groups, are little discussed. But this is, overall, a scholarly book providing a possible explanation of autism. It will be of interest to parents as well as professionals.

Lathe's story stands in marked contrast to Understanding Autism, a volume edited by Steven Moldin and John Rubenstein. This excellent collection of chapters on ASD, and on basic research relevant to ASD, provides few answers, but, I fear, better reflects the truth about our understanding of autism. A detailed and thorough examination of epidemiological studies by Eric Fombonne, for example, casts real doubt on the claim that the rate of ASD cases is increasing. Instead, he concludes that truly comparable time-trend data do not exist; until these are collected, changes in diagnostic criteria and practices, greater awareness and improved services may be sufficient to explain the increase in identified cases. And if there is no big rise in prevalence, there is no need to invoke a major environmental contribution.

Similarly, the idea that autism can be explained by damage to the limbic system (the 'social brain') is probably too simplistic. The chapter by Schumann, Bauman, Machado and Amaral reviews evidence from human and animal lesion studies. They suggest that the amygdala is not the seat of social processing, but instead plays a role in regulating fear behaviour, with knock-on effects exacerbating social deficits in autism. Indeed, many examples in the book illustrate how much more complex the story of autism is likely to be, including epigenetic regulation (not involving differences in the nucleotide sequence) through DNA methylation or chromatin remodelling.

Should we be despondent in the face of such complexity and the paucity of answers regarding the causes of autism? I think the book by Moldin and Rubenstein gives as much reason for hope as for despair. The chapters reflect the diverse tools being called into the service of understanding autism, including neuroimaging, animal models, even the use of neurotropic viruses, which attack the nervous system, to trace chains of synaptically linked neurons.

Parents, teachers, clinicians and researchers are all searching for explanations, for a story that will help us make sense of autism and show us how to help. Lathe's book tells a fascinating tale, but Moldin and Rubenstein's may be closer to the truth. After all, the one thing that all those who study autism agree on is that no one really understands autism.