| Autism, is it in the genes - is there a connection? Bright Tots - Information on child development - Autism information. |
| Autism. Is it in the Genes? |
| Autism. Is it in the Genes |
Research suggests that the number of people affected by ASD may have doubled over the last decade. The number of cases of autism could be four times higher than previously estimated, warned scientists. The number of diagnoses seems to be on the increase, but some argue this is simply because of a greater awareness of the condition.
Even autism experts who suspected that existing studies had produced overly conservative results said that the latest findings were unexpectedly high. It affects about five in 10,000 people, predominantly boys, and is often also associated with learning disabilities. The study also found that "pervasive developmental disorders" which fall short of the strict diagnostic criteria for autism were running at a rate of nearly 46 per 10,000.
Genetics May Cause Autism
Genes are very small pieces of hereditary material, meaning that parents pass them on to their children. Every person gets half their genes from their mother and half from their father.
The pattern, or sequence, of your genes is like a blueprint that tells your body how to build its different parts. Your gene sequence controls how tall you are, what color your hair and eyes are, and other features of your body and mind. Changes in that blueprint can cause changes in how your body or mind develops. Genes are found on chromosomes. Almost every cell in your body contains 23 pairs of chromosomes, 46 in all. Genes and chromosomes give the body all the information it needs to “build” a person.
Experts have noted that the condition has a strong genetic component, evidence suggests that autism can be caused by a variety of physical factors, all of which affect brain development . The number of children with autism appears to be increasing more than expected for a genetic disorder. Scientists say they have identified a gene which may increase the risk of developing autism. There is growing evidence that the condition may be inherited. Studies suggest parents with one child with autism are 100 times more likely to have another child with the condition compared with other families. However, scientists agree that the condition is complex and that more than one gene is involved.
The American Journal of Psychiatry, they said as many as 10 different genes might be involved in the development of autism. Other researchers have been attempting to identify genes predisposing people to autism, which are thought to be as many as 20. Identifying all or most of the genes involved will lead to new diagnostic tools and new approaches to treatment. Scientists over the world are engaged in looking for the genetic roots of autism.
Families Share Autistic Traits
Relatives of people with autism may display autistic brain differences and behaviors despite not having the condition themselves, a study shows. Experts hope it could help in the quest to find genetic and environmental triggers for the condition,. Autism is a disorder that makes it hard for the individual to relate socially and emotionally.
Family histories and family studies show that some of the autism-like symptoms, such as delays in language development, occur more often in parents or adult brothers and sisters of people with autism, than in families who have no autistic members or relatives. Because members of the same family have similar gene sequences, these studies suggest that something about gene sequences is linked to autism. Autism is a spectrum disorder, meaning people with autism can have a range of symptoms. A certain change in the gene sequence may make the condition very mild, so that a person doesn't have autism, but has one of its symptoms instead. A different change in that sequence could make the symptoms of autism more serious.
Based on these findings, doctors have long felt that a link between genes and autism was a strong
possibility. A study, led by the University of Wisconsin-Madison Medical School, showed that the amygdala, a brain region involved in processing emotions, was shrunken in both autistic children and their sibling. The siblings also avoided eye contact, a common feature of autism, just as strongly as their affected siblings even though they did not have autism themselves.
Professor Simon Baron-Cohen, director of the Autism Research Centre said “first-degree relatives, parents or siblings of those with autism, may have some but not all of those genes. This would explain why they do not have autism but do show some milder manifestations. We have known for years that family members of people with autism may share some traits. It is telling us that these genes, as they run through families, are affecting brain function and structure not just in the person with autism but also in their first degree relatives." Genetic testing to diagnose a pre-disposition to an autistic spectrum disorder was not, at present, possible because there were too many genetic and environmental factors involved in the condition.
Autism in Twins
When autism occurs in identical twins, both members of the set have the condition 60 percent of the time. When autism occurs in fraternal twins, both members of the set have the condition only 3 to 6 percent of the time. Identical twins come from a single egg that splits in two, so they share 100 percent of their genes. Fraternal twins come from two separate eggs, so they are genetically different. If autism was not caused in part by genes, then the number of identical twins with autism would not be any higher than the number of fraternal twins with the condition. But, since both identical twins have autism more often than both fraternal twins do, researchers think that genes play a role in autism.
Due to differences in peoples’ symptoms, researchers believe that autism is the result of many genes interacting with each other. At this point, it seems that some children are born with a genetic susceptibility to autism. What makes some susceptible individuals develop autism and others not is an important research question
Brain Inflammation linked to Autism
Scientists have produced compelling evidence that autism may in some cases be linked to inflammation of the brain. They found certain immune system components that promote inflammation are consistently activated in people with autism. It’s possible that inflammation was produced as a result of the brain trying to combat some other process damaging to brain cells. In recent years, there have been scientific hints of immune system irregularities in children with autism, but not all studies have confirmed this.
A spokesperson for the National Autistic Society said other scientists had also examined the possible connection between the immune system and autism. One study has linked the condition to the disease encephalitis, while another found raised levels of nitric oxide in the plasma of children with autism. This chemical plays a role in the immune response, and which is known to affect neuro-developmental processes.
Compared with normal control brains, the brains of the people with autism were found to contain abnormal patterns of immune system proteins consistent with inflammation. Researchers say these findings reinforce the theory that immune activation in the brain is involved in autism, although it is not yet clear whether it is destructive or beneficial, or both, to the developing brain.
Possible Causes
Research has also linked the condition with a variety of conditions affecting brain development which occur before, during, or very soon after birth. The CDC team found children with autism were more likely to have had difficult births than other children of the same age. This included breech births, premature births and problems immediately after delivery.
Parental psychiatric history was associated with the highest independent risk of autism. However, none of these factors were present in the vast majority of the autistic children, other factors must also be important, said the researchers. A spokesman from the CDC said: "At this point, we don't know for sure if these events are causes, but it certainly points us to look more closely at what happens during pregnancy as a possible opportunity for future prevention."
The National Autistic Society said: "The causes of autism are still being investigated. Many experts believe that the pattern of behavior from which autism is diagnosed may not result from a single cause.” Toxins, diet, viruses and other pathogens have been suggested, though there is no strong evidence for any of these. There is strong evidence to suggest that autism can be caused by a variety of physical factors, all of which affect brain development, it is not due to emotional deprivation or the way a person has been brought up. The causes of autism and PDD are unknown. It’s a complex biological disorder, and no two people with autism are the same. These differences lead scientists to believe that autism is the result of a mixture of causes.
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