More than half of all cases of autism are caused by environmental factors, and genetics accounts for just 37 per cent of cases, researchers have discovered this week - far different from the current model that puts inheritance as the primary cause, thought to account for 90 per cent of all cases.
Researchers from Stanford University made the discovery when they examined the histories of 1,156 twins with at least one suffering from autism - which alone suggests that genetics has little to do with the condition.
One environmental cause could be antidepressants that were taken by the mother, especially during the first trimester. Researchers from Kaiser Permanente Northern California discovered that the drug more than doubles the risk of autism, especially if the mother was taking the drugs before conception or early in the pregnancy.
(Sources: Genetics study: Archives of General Psychiatry, 2011; doi: 10.1001/archgenpsychiatry.2011.76; antidepressants study: Archives of General Psychiatry, 2011; doi: 10.1001/archgenpsychiatry.2011.73).