Autism incidence

Data from an earlier study have been reanalysed to test the hypothesis that MMR vaccine might cause autism but that the induction interval needs to be short (495). Evidence for an increased incidence was sought using the case-series method. The study used data on all... 

Controversially, some have claimed a connection between the use of thimerosal in vaccines and the apparent rise in the incidence of autism. However, recent studies have shown no association between thimerosal exposure and autism. ... 

What do Gulf War Syndrome, Katrina Cough, Aerospace Syndrome, and epidemic increases in the incidence of autism, Attention Deficit Hyperactivity Disorder (ADHD), birth defects, asthma, mailroom illness, spontaneous abortion, and many cancers have in common Each of these can be associated with a single causative agent, but each can also be associated with environmental exposure to chemical mixtures that do not contain any of the known causative agents. 

There are no known direct studies on the toxic effects of chemical exposures on the developing fetus. It is known, however, that children of tobacco smokers (tobacco smoke is a mixture of multiple lipophiles and hydrophiles) have unusually high incidences of ADHD, autism, and other developmental disorders. These and other mixture effects are examined more closely in subsequent chapters. This chapter has aimed to alert the reader to the fact that toxic exposure begins at conception and impacts the fetus throughout gestation and beyond. 

The earliest of these developmental abnormalities involve the brain stem. In a unique case, Rodier et al. (1996) reported the nearly complete absence of the superior olive and facial nerve nucleus, with shortening of the brain stem between facial nerve nucleus and the trapezoid body. They concluded that the initiating injury in this autistic brain occurred around the time of neural tube closure, which occurs at about 4 weeks of fetal development (O Rahilly and Muller, 1994). This timing also corresponds to an increased incidence of autism following exposure to the drug thalidomide during pregnancy (Rodier and Hyman, 1998 Miller et al., 2005). 

As a result of these difficulties, only a few of the medications commonly employed for treatment of autism spectrum disorders (ASD) have been subjected to randomized, double-blind, placebo-controlled studies. Most published studies are uncontrolled, open-label studies of small numbers of patients. Because of the high incidence of response to placebo frequently observed in controlled studies of autism therapies (Aman et al., 2005 Sandler et al., 1999 Belsito et ah, 2001 Sandler, 2005), open-label studies are frequently misleading and are of little value for assessing treatment effectiveness, although they can be useful for identifying serious adverse effects. 

A positive association exists between mothers who live near organochlorine pesticide use and the incidence of autism in offspring.75 The incidence declines with increasing distance from agricultural fields that use such pesticides. 

Previc, F. H. (2007). Prenatal influences on brain dopamine and their relevance to the rising incidence of autism. Med. Hypotheses. 

The neurohypophyseal hormones oxytocin and vasopressin are involved in autism. Elevated levels of blood serotonin occur in one third to two thirds of persons with autism. Parents of autistic children often have elevated blood serotonin levels, as well as an increased incidence of depression, obsessions, and compulsions. 

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