Physical cause of autism, and underlying mechanisms remain largely unexplained

[astro]

Autism - Interesting, I thought we had a better handle on it than this. It’s amazing how much we don’t know.

[astro]

Forgot wiki quote

It has long been presumed that there is a common cause at the genetic, cognitive, and neural levels for autism’s characteristic triad of symptoms.[58] However, there is increasing suspicion that autism is instead a complex disorder whose core aspects have distinct causes that often co-occur.[58][59]

Deletion (1), duplication (2) and inversion (3) are all chromosome abnormalities that have been implicated in autism.[60]Autism has a strong genetic basis, although the genetics of autism are complex and it is unclear whether ASD is explained more by rare mutations with major effects, or by rare multigene interactions of common genetic variants.[4][61] Complexity arises due to interactions among multiple genes, the environment, and epigenetic factors which do not change DNA but are heritable and influence gene expression.[16] Studies of twins suggest that heritability is 0.7 for autism, and 0.9 for the broader autism phenotype.[36] However, most of the mutations that increase autism risk have not been identified. Typically, autism cannot be traced to a Mendelian (single-gene) mutation or to a single chromosome abnormality like fragile X syndrome, and none of the genetic syndromes associated with ASDs has been shown to selectively cause ASD.[4] Numerous candidate genes have been located, with only small effects attributable to any particular gene.[4] The large number of autistic individuals with unaffected family members may result from copy number variations—spontaneous deletions or duplications in genetic material during meiosis.[62] Hence, a substantial fraction of autism cases may be traceable to genetic causes that are highly heritable but not inherited: that is, the mutation that causes the autism is not present in the parental genome.[60]

Some rare mutations may lead to autism by disrupting some synaptic pathways, such as those involved with cell adhesion.[63] Gene replacement studies in mice suggest that autistic symptoms are closely related to later developmental steps that depend on activity in synapses and on activity-dependent changes.[64] All known teratogens (agents that cause birth defects) related to the risk of autism appear to act during the first eight weeks from conception, and though this does not exclude the possibility that autism can be initiated or affected later, it is strong evidence that autism arises very early in development.[5] Although evidence for other environmental causes is anecdotal and has not been confirmed by reliable studies,[6] extensive searches are underway.[65] Environmental factors that have been claimed to contribute to or exacerbate autism, or may be important in future research, include certain foods, infectious disease, heavy metals, solvents, diesel exhaust, PCBs, phthalates and phenols used in plastic products, pesticides, brominated flame retardants, alcohol, smoking, illicit drugs, vaccines,[8] and prenatal stress.[66] Parents may first become aware of autistic symptoms in their child around the time of a routine vaccination, and this has given rise to theories that vaccines or their preservatives cause autism. Although these theories lack convincing scientific evidence and are biologically implausible, parental concern about autism has led to lower rates of childhood immunizations and higher likelihood of measles outbreaks.[7]

There is no known single cause for autism, but it is generally accepted that it is caused by abnormalities in brain structure or function. Brain scans show differences in the shape and structure of the brain in children with autism versus neuro-typical children. Researchers are investigating a number of theories, including the link between heredity, genetics and medical problems. In many families, there appears to be a pattern of autism or related disabilities, further supporting a genetic basis to the disorder. While no one gene has been identified as causing autism, researchers are searching for irregular segments of genetic code that children with autism may have inherited. It also appears that some children are born with a susceptibility to autism, but researchers have not yet identified a single “trigger” that causes autism to develop.

Other researchers are investigating the possibility that under certain conditions, a cluster of unstable genes may interfere with brain development, resulting in autism. Still other researchers are investigating problems during pregnancy or delivery as well as environmental factors, such as viral infections, metabolic imbalances, and exposure to environmental chemicals.

[Spice_Weasel]

My husband is taking a neurobiology class right now.

One of the units is entitled: ‘‘Autism: So Many Theories, So Little Hope.’’

[AboutAsWeirdAsYouCanGet]

Deletion (1), duplication (2) and inversion (3) are all chromosome abnormalities that have been implicated in autism

One thing that REALLY irritates me is when “autistic-like”/ non nereotypical
behavoirs are ALL lumped in with autism.
I have a chromosome deletion…and while I have some not exactly nereotypical behaivors, they are NOT autistic per se. More like along the lines of someone with ADD or LD or whatever.

[Markxxx]

I saw an Elvis movie and he cured a girl with autism