Early environmental factors in autism

Abstract

Genetic and environmental influences are not mutually exclusive as causes of birth defects. Rather, both contribute to the etiology of many congenital anomalies. Recent results from studies of autism in twins argue that this is the case for autism spectrum disorders. Thus, even after the genetic causes of autism are known, it will be necessary to identify environmental factors that contribute to the expression of the symptoms. The first half of this review describes what has been learned from research on exogenous influences in autism, discussing studies of infections, inoculations, general pre-and perinatal factors, family histories, and drug and chemical exposures. The second discusses gene-environment interactions in other birth defects and the methods by which teratogens have been discovered. The role of known genetic syndromes in the etiology of autism is discussed with attention to whether their associations with the disorder are genetic or teratologic in nature.

The Time of Prenatal Immune Challenge Determines the Specificity of Inflammation-Mediated Brain and Behavioral Pathology

“…It is important to emphasize that we did not observe any sign of neurodegeneration that is typified by the presence of necrotic cell loss and reactive gliosis. The absence of gross brain anatomical alterations agrees well with the hypothesis that neurodevelopmental disturbance rather than neurodegeneration is central to the etiopathogenesis and disease process of schizophrenia and autism (Weinberger, 1987;Rodier and Hyman, 1998;Arndt et al, 2005;Miller et al, 2005;Rapoport et al, 2005).…”

“…One implication is that the precise timing may underlie the relationship between the differing neurodevelopmental vulnerability associated with in utero infection and the etiopathogenesis of mental disorders with a presumed developmental origin. This may also determine whether the eventual psychological profile falls into one or another subtype category, given that different subtypes of a psychiatric disease are likely to be associated with distinct neurodevelopmental failures (Murray et al, 1992;Rodier and Hyman, 1998;Sporn et al, 2004). method; the bars correspond to the minus and plus range of the fold changes.…”

Autism Spectrum Disorders in Relation to Distribution of Hazardous Air Pollutants in the San Francisco Bay Area

“…Prior studies have reported associations of autism with maternal smoking ( Hultman et al 2002 ), heavy alcohol consumption ( Aronson et al 1997 ), some prescription medications ( Moore et al 2000 ; Stromland et al 1994 ), and parental occupations involving chemical exposures (reviewed by Allred and Wilbur 2002 ). These observations, combined with those from animal and neuroimaging studies, suggest that exposures early in gestation, around the time of neural tube closure, may be most critical ( Rodier and Hyman 1998 ). A strong genetic component is indicated in the etiology of autism; it has been hypothesized this could involve susceptibility genes that, when combined with exposure, lead to this condition ( London and Etzel 2000 ).…”

Measles-Mumps-Rubella Vaccine and Autistic Spectrum Disorder: Report From the New Challenges in Childhood Immunizations Conference Convened in Oak Brook, Illinois, June 12–13, 2000

“…Many factors have been proposed, including infection, aberrant immune response, and exposure to teratogens at critical periods of neurologic development. 54 Maternal ingestion of thalidomide resulted in a dramatic increase in risk of ASD if exposure occurred in a discrete time period during the first month of gestation. 55 Knowledge of this timing led to the identification of the relationship between autism and the HOXA1 gene, which participates in the regulation of brainstem development at this stage of gestation.…”