| Autism genetic research has shown that it is one of | | | | Many family studies have been conducted as well. A |
| the most heritable disorders. Despite an increasing | | | | Danish study in 2005 looked at risk aspects of the |
| amount of autism genetic studies being performed | | | | entire family. If the autistic child had Asperger's |
| each year the researchers are still trying to discover | | | | syndrome the risk for other children to have some |
| the multiple genes believed to be the reason for | | | | type of autism was believed to be 1.04% while if the |
| autism. | | | | child had other forms of autism the feeling was a risk |
| There have been numerous studies, completed and | | | | factor of 1.76%. These risk factors were double if the |
| ongoing, on twins and siblings. Identical twins, who share | | | | mother had ever been diagnosed with any form of |
| one hundred percent of their nuclear DNA, where one | | | | psychiatric disorder. These conclusions were formed |
| has autism, have about a sixty percent chance of the | | | | after a thorough study of the entire family including |
| second child having autism and a ninety percent | | | | collecting information on the parent's place of birth, their |
| chance of the identical twin having some type of | | | | age, the location the child/children were born, and the |
| autistic spectrum disorder. With fraternal twins, where | | | | family history for depression or psychiatric difficulties. |
| the genes shared number only fifty percent, the | | | | Although paternal age seemed to be an issue, |
| chance of the second twin being autistic lowers | | | | maternal age was not. |
| dramatically to four and half percent, just like it would | | | | These studies have left almost as many questions |
| with any sibling. For the average person the chance of | | | | unanswered as they have answered. If identical twins |
| having autism is .2%. These numbers speak strongly in | | | | show such an increase in heritability why don't fraternal |
| favor of evidence that links autism with heritability. | | | | twins? Why are parents of autistic children almost |
| Autism genetic studies of twins have been going on | | | | always people who do not have autism if heritability is |
| since the middle 1970s. Of nine studies conducted | | | | so definitely a factor in this disorder? Some |
| worldwide between 1977 and 2004 all of them came | | | | researchers question if autism has become the word |
| to relatively the same conclusion regarding identical | | | | of its time and perhaps too many children are being |
| twins and the chances of a second twin having autism. | | | | lumped into this group for ease of diagnosis. All these |
| One study felt that the delivery highly influenced the | | | | unanswered questions will only be answered once |
| chance of an autistic child, but overall the conclusions | | | | more studies into the heritability of autism are |
| were very similar. | | | | conducted and results are known. |