Etiology of Autism

Internet Resources

While we do not at present know the neuroanatomical origin of autism, we know much about what it must look like. Prefrontal neocerebellum disconnection will grossly affect cognition in rather peculiar ways resembling autism.
John Skoyles
Allergies or asthma during pregnancy may increase the risk of giving birth to a child who develops autism... Although the causes of autism are not well understood, genetic predisposition is considered to play a major role. A few environmental triggers have also been identified, including prenatal exposure to certain chemicals.
Salynn Boyles, FOX News
This work provides general results from all of the data collected and combines results for certain areas of interest, such as autism causation by decade or the types of causations being investigated from one country to the next.
Jeff and Cathy Romanczuk
Journal of Autism and Childhood Schizophrenia 1971 Jan-Mar;1(1):33-47
Stella Chess
Not all autistics have cerebellar features identical to those described by Bauman/Kemper; lack of gliosis does not necessarily imply in-utero timing of altered cerebellar morphology; not all autisms are in-utero with regard to timing of causality.
Teresa Binstock
Objective: To explore possible associations between autism spectrum disorders (ASD) and environmental exposures, we linked the California autism surveillance system to estimated hazardous air pollutant (HAP) concentrations compiled by the U.S. Environmental Protection Agency. Methods: Subjects included 284 children with ASD and 657 controls, born in 1994 in the San Francisco Bay area. We assigned exposure level by census tract of birth residence for 19 chemicals we identified as potential neurotoxicants, developmental toxicants, and/or endocrine disruptors from the 1996 HAPs database. Because concentrations of many of these were highly correlated, we combined the chemicals into mechanistic and structural groups, calculating summary index scores. We calculated ASD risk in the upper quartiles of these group scores or individual chemical concentrations compared with below the median, adjusting for demographic factors. Results: The adjusted odds ratios (AORs) were elevated by 50% in the top quartile of chlorinated solvents and heavy metals [95% confidence intervals (CIs) , 1.1-2.1], but not for aromatic solvents. Adjusting for these three groups simultaneously led to decreased risks for the solvents and increased risk for metals (AORs for metals: fourth quartile = 1.7 ; 95% CI, 1.0-3.0 ; third quartile = 1.95 ; 95% CI, 1.2-3.1) . The individual compounds that contributed most to these associations included mercury, cadmium, nickel, trichloroethylene, and vinyl chloride. Conclusions: Our results suggest a potential association between autism and estimated metal concentrations, and possibly solvents, in ambient air around the birth residence, requiring confirmation and more refined exposure assessment in future studies.
Gayle C. Windham; Lixia Zhang; Robert Gunier; Lisa A. Croen; Judith K. Grether
In general, the incidence of autism has paralleled the incidence of immediate cord clamping, and supports the conclusion that autism results from birth asphyxia caused by immediate cord clamping.
George Malcolm Morley
On the genetic risk for autism, the MMR issue, and the nature of autistic mentalizing, , involving the dimensions of systemizing and empathizing.
Mike Connor
Until the causes of autism are clearly identified parents will continue to be blamed by well meaning professionals for a lack of parenting skills, and will continue to try each new cure of the month.
Joy Wilson
Although Autistic Disorder is associated with several congenital conditions, the cause for most cases is unknown. The present study was undertaken to determine whether breastfeeding or the use of infant formula supplemented with docosahexaenoic acid and arachidonic acid is associated with Autistic Disorder. The hypothesis is that breastfeeding and use of infant formula supplemented with docosahexaenoic acid/arachidonic acid are protective for Autistic Disorder. This is a case-control study using data from the Autism Internet Research Survey, an online parental survey conducted from February to April 2005 with results for 861 children with Autistic Disorder and 123 control children. The analyses were performed using logistic regression. Absence of breastfeeding when compared to breastfeeding for more than six months was significantly associated with an increase in the odds of having autistic disorder when all cases were considered and after limiting cases to children with regression in development. Use of infant formula without docosahexaenoic acid and arachidonic acid supplementation versus exclusive breastfeeding was associated with a significant increase in the odds of autistic disorder when all cases were considered and after limiting cases to children with regression in development. The results of this preliminary study indicate that children who were not breastfed or were fed infant formula without docosahexaenoic acid/arachidonic acid supplementation were significantly more likely to have autistic disorder.
Stephen T. Schultz et al
A recent news story puts forth the claim; batteries from mobile phones and iPods have been linked to autism. Orac asks some good questions about the story and the scientists quoted in the article here. From what I can tell, mercury isn't lithium-ion batteries used to power cellphones and portable MP3 players. I understand concerns about the fate of other potentially toxic components found in modern electronic devices so I decided to disassemble my own cellphone to see if there is anything in there that might cause autism.
Not Mercury
It is gratifying to see that research into the causes of autism has helped to temper the guilt so often experienced by parents when the disorder was considered to be psychogenic in origin. However, the difficulty of conducting sound studies of causation has now led some healthcare practitioners to encourage parents to act on very poor quality data and vigorously pursue hypothetical causes.
Peter Szatmari, British Medical Journal
Journal of Autism and Childhood Schizophrenia 1971 Jan-Mar;1(1):20-32
Michael Rutter
It is becoming more and more likely that Autism is the result of a combination of factors which come into play in approximately 1 in 500 children
Adelle Jameson Tilton
In new research, scientists have found that a specific gene contributes to autism and that autistic people have fewer receptors for the brain messenger acetylcholine, as well as more tightly packed columns of neurons in the cerebral cortex. Another study found that autistic children were less able to discriminate similar sounds than were other children. The research is providing new clues to the genetic, neurological, and molecular basis of this still mysterious disease. (Note from web site owner: In my personal opinion as an autistic person, and that of many other adults autistics, autism is not necessarily "devastating." There are hundreds of thousands of people with autism who are not devastatingly disabled, although they may have patterns of disability labeled as "Asperger's Syndrome," "High Functioning Autism," or "Pervasive Developmental Disorder." Most people with autism are not mentally retarded, either.)
Society for Neuroscience
New data from developmental genetics, behavioral studies, brain imaging and many other sources can be expected to produce more welcome shocks of recognition for investigators of autism.
Patricia Rodier
Although many scientists have long known that autism is an inherited disease, recent family studies suggest that it is the spectrum of symptoms that runs in families rather than a single diagnosis.
Patricia Rodier
Many symptoms of autism are most easily explained by brain stem malfunctions. Eye motility abnormalities, hyper-acute hearing, lack of facial expression, unusual sensitivities to food taste and texture, hypersensitivity to touch, oddities of gait, hearing deficits and synesthesias (sensory crossings-over, such as a sound being perceived as a color) -- all have been cited as characteristics more common in autistic than in non-autistic populations. While each of these symptoms could be effected by damage to several different levels of the nervous system both "high" and "low," the simplest explanation is that they result from an injury to the brain stem.
Patricia M. Rodier
Reviews the recent literature on possible causes of the increase in frequency of diagnosed autism reported from three countries, and compares the medical diagnoses and drug therapy.
Hershel Jick, James Kaye
Michael I.Shevell , Annette Majnemer, Peter Rosenbaum, Michal Abrahamowicz
Autism and Asperger Syndrome is caused by deficiencies in cognitive modules relating to language, social intelligence and our ability to form abstract concepts from concrete literals.
Steve McKinlay
The fields of neuroanatomy, neurochemistry, and genetics have each offered different avenues in uncovering some of the mysteries linked to the etiology of autism.
Michele Roig
Autism is caused by a pathophysiologic process arising from the interaction of an early environmental insult and a genetic predisposition.
Geneviève Trottier, Lalit Srivastava, Claire-Dominique Walker
Thus far, each kind of evidence we have collected supports the hypothesis that the autism spectrum disorders are initiated by brain stem injury during early development. An animal model in which embryos are exposed to valproic acid during neural tube closure reproduces the cranial nerve anomalies predicted by the neurological dysfunctions of thalidomide-induced autism. It also parallels the cerebellar anomalies reported in human histology and MRI.
Patricia M. Rodier
Research in the last 2 decades indicates that autism is largely caused by genetic factors that lead to abnormal brain development. This article reviews research into the genetic and neurodevelopmental factors underlying autism.
Rob Nicolson, Peter Szatmari
Byrd recently confirmed that the incidence of autism is increasing dramatically. The image-of-the-eyes hypotheses suggest that this increase may be due to the increased use, in early infancy, of non-maternal childcare including television and video.
Maxson J. McDowell
The narrower the behavioural definition of a developmental disorder, the more likely it is that the disorder will have multiple underlying causes.
Michael S. C. Thomas
Autism represents a severe developmental disturbance of the brain that most likely occurs at the late or end stages of brain development.
Roland Ciaranello
While some parents report the onset of autism following vaccination, others say antibiotics were the trigger, introduction of certain foods, earaches, acetaminophen, etc. Any thing that may be introduced around the time of regression or initial diagnosis can be blamed, even though millions of children are exposed to the same things without becoming autistic. Don't worry, we have a partial genetic explanation to explain this: "Some children are born with a genetic susceptibility to ________ which leaves them unable to handle certain substances......" Doesn't that sound like an argument for more investment in genetic research?
Not Mercury
Certainly genes play a causative role in autism, ample evidence has revealed. However, perinatal complications or certain variables, such as older maternal age, may also be culprits, studies of the past 30 years have suggested. Nonetheless, findings regarding perinatal complications have been inconsistent and often contradictory because of variations in sample size, data quality, control groups, and so forth. Thus, Australian researchers decided to use centralized resources in Western Australia to conduct a large population-based study on possible perinatal factors contributing to autism. As they reported in the June Archives of General Psychiatry, they have found what previous studies have generally foundómothers of individuals with autism are more likely to have experienced difficulties during pregnancy, labor, and delivery than mothers of persons without autism.
Joan Arehart-Treichel, Psychiatric News
Men who become fathers in their 40s or older are much more likely to have autistic children than younger dads, a new study released Monday shows, bolstering evidence that genetics contributes to the mental disorder. The research involved about 130,000 Israeli Jews born in the 1980s. Those fathered by older men were almost six times more likely to have autism or related disorders than those fathered by men younger than 30, and more than one and a half times more likely than children fathered by men ages 30-39.
Lindsey Tanner, The State
Children with older fathers have a significantly increased risk of having autism, a study has concluded. The UK and US researchers examined data on 132,271 children and said those born to men over 40 were six times more at risk than those born to men under 30. They said the study in Archives of General Psychiatry was further proof men also had "biological clocks". One UK expert said the study could be important in understanding the genetic mechanisms underlying autism.
British Broadcasting Corporation
The values of patriarchal social structures are the values of most contemporary societies. Only in the last two generations has that begun to change. One of the results of these recent changes is the rise in autism. Many things are changing. Three forces in particular are propelling children in the direction of maturational delay: Environmental Variables; Contemporary Sexual selection Practices; Blending of Ethnic Persuasions.
New research with rats suggests that oxygen deprivation during birth could be a contributing cause of autism. By boosting the level of nitrogen in the air, Strata and colleagues deprived rat pups of normal levels of oxygen for as long as 10 to 12 minutes during birth. When the rats grew older, they displayed symptoms similar to those found in autistic children. It took longer for the rats to respond to some sounds, for example, and the brain regions that handle sound were disrupted.
We conducted systematic observations of the social interactions of two matched groups of congenitally blind children who do not have autism, rating their social engagement, emotional tone, play and language during three sessions of free play in the school playground. The qualities of social impairment in the more disabled children were similar to those in sighted children with autism.
R. Peter Hobson, Martin Bishop
Risk of autism was associated with smoking in early pregnancy, maternal birth outside Europe or North America, Caesarian delivery, small for dates, low Apgar and congenital malformations. The implications are that intrauterine and neonatal factors are important factors for autism.
In studying archived placental tissue of 13 children affected by autism spectrum disorder (ASD) and 61 unaffected children, researchers found a distinctive microscopic morphological abnormality -- placental trophoblast inclusions -- significantly more often in the autistic children. "Although probably not functionally detrimental or causative, the greater occurrence of placental trophoblast inclusions observed in ASD individuals may reflect altered early developmental processes," writes the study team in the June 26th online issue of Biological Psychiatry. "Placental trophoblast inclusions, which are actually abnormalities in the way the placenta folds and grows, could be an early marker of autism," Dr. Harvey J. Kliman, from the department of obstetrics, gynecology and reproductive sciences at Yale University School of Medicine in New Haven, Connecticut noted in an interview with Reuters Health.
Megan Rauscher, Medscape
The results of this study support previous findings suggesting a consistent association of unfavorable events in pregnancy, delivery, and the neonatal phase and the pervasive developmental disorders. However, interpretation of the meaningfulness of these results is difficult, as the specific complications that carried the highest risk of autism and PDD-NOS represented various forms of pathologic processes with no presently apparent unifying feature.
Naya Juul-Dam, Jeanne Townsend, Eric Courchesne
This review makes it excruciatingly clear that only the most preliminary data are currently available on the neurological basis of autism and that no coherent theory is at hand, although progress has begun.
Federation Quebecoise de l'Autisme
In this study we found that nearly every other VLBW (very low birth weight) adolescent had psychiatric symptoms. One in four had a psychiatric diagnosis, anxiety disorders being the most prevalent. Attention deficit problems were acknowledged in every fourth VLBW adolescent, but only a minority fulfilled the diagnostic criteria. Moreover, relational problems and deficits in social skills were common among VLBW adolescents, and some had autistic spectrum symptoms. Although every fifth SGA adolescent had psychiatric symptoms, they did not differ significantly from controls.
M.S. Indredavik
If we are marrying and having our children later, and men are much, much more likely to be working alongside women, because of a greater degree of equality within the job market and a decline of those jobs traditionally associated with women, is it not possible that these days our partners would tend to be drawn from the sphere of work rather than, as before, in a rather more random fashion from within our home communities?
Rod Liddle, Spectator
Dr Richard Lathe, a specialist in childhood Autism, and former professor at Edinburgh University is claiming in a forthcoming paper that incorrect disposal of rechargeable batteries is one of the factors in an increase in autism in the UK. Autistic children have been shown to have problems getting rid of toxic metals - and those metals are increasingly polluting the environment, says Dr Richard Lathe.
Cellular News
Research suggests that heredity and early fetal development play a causal role in autism. This case-control study explored the association between perinatal factors, parental psychiatric history, socioeconomic status, and risk of autism. The study was nested within a cohort of all children born in Denmark after 1972 and at risk of being diagnosed with autism until December 1999. Results suggest that prenatal environmental factors and parental psychopathology are associated with the risk of autism. These factors seem to act independently.
Heidi Jeanet Larsson, William W. Eaton, Kreesten Meldgaard Madsen, Mogens Vestergaard, Anne Vingaard Olesen, Esben Agerbo, Diana Schendel, Poul Thorsen, Preben Bo Mortensen
New findings indicate a deficiency in the coordination among brain areas. The results converge with previous findings of white matter abnormalities in autism. White matter consists of the "cables" that connect the various parts of the brain to each other.
Medical News Today
Recognition that a range of symptoms is associated with autism has forced psychiatrists to change the way that they define the condition. These diagnostic changes may explain the rise in the number of recorded cases of autism.
Kathleen Wong, Nature
Even the most promising treatments for autism rest on an insufficient research base, and are sometimes inappropriately and irresponsibly promoted as 'cures.'
James D. Herbert, Ian R. Sharp, Brandon A. Gaudiano
We argue that there will be no single (genetic or cognitive) cause for the diverse symptoms defining autism. We present recent evidence of behavioral fractionation of social impairment, communication difficulties and rigid and repetitive behaviors. Twin data suggest largely nonoverlapping genes acting on each of these traits. At the cognitive level, too, attempts at a single explanation for the symptoms of autism have failed. Implications for research and treatment are discussed.
F. Happe et al
t occurred to Cornell University management professor Michael Waldman, PhD, that the increase in autism cases came at the same time as increased opportunities for very young children to watch TV. Could it be, he wondered, that the explosion in children's TV programming, DVDs, VCRs, and video/computer games is behind the explosion in autism diagnoses? Waldman asked his colleagues in the medical world to look at the issue. Nobody would. So he assembled a research team and did the study himself -- using tools more often seen in economic studies than in medical studies. The results bolstered his suspicions.
Daniel DeNoon, Medscape
It is clear that children with autism and PDD are born with the disorder or born with the potential to develop it. It is not caused by bad parenting. Autism is not a mental illness.
Existing research suggests that multiple, interacting genes are involved in the causation of autism. The developing child's social environment has not been found to cause autism. However, a proper behavioral-educational environment can significantly improve outcome.
Ira L. Cohen

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