The following information is not intended to diagnose or treat. It should not take the place of consulting a qualified healthcare professional.
A common question after an autism diagnosis is what causes autism.
We know that there is no single cause of autism. Research suggests that autism develops from a combination of genetic and non-genetic or environmental influences.
These influences appear to increase a child's risk of developing autism. However, it is important to note that an increased risk is not the same as a cause. For example, some genetic changes associated with autism can also be found in people who do not have the disorder. Similarly, not all people exposed to an environmental risk factor for autism will develop the disorder. In fact, most will not.
Genetic risk factors for autism
Research tells us that autism tends to run in families. Changes in certain genes increase a child's risk of developing autism. If a parent carries one or more of these genetic changes, it is possible for them to be passed on to a child (even if the parent does not have autism). Other times, these genetic changes arise spontaneously in an early embryo or in the sperm and / or egg that combine to create the embryo. Again, most of these genetic changes do not cause autism on their own. They simply increase the risk of developing the disorder.
Environmental risk factors for autism
Research also shows that certain environmental influences can further increase or reduce the risk of autism in people who are genetically predisposed to the disorder. Importantly, the increase or decrease in risk appears to be small for any of these risk factors:
Increased risk
Advanced age of parents (either parent)
Complications of pregnancy and delivery (for example, extreme prematurity [before 26 weeks], low birth weight, multiple pregnancies [twins, triplets, etc.])
Pregnancies less than a year apart
Decreased risk
Prenatal vitamins that contain folic acid, before and during conception and during pregnancy
No effect on risk
Vaccinations Each family has a unique experience with an autism diagnosis, and for some it corresponds to the timing of their child's immunizations. At the same time, scientists have done extensive research over the past two decades to determine if there is any link between childhood vaccines and autism. The results of this research are clear: vaccines do not cause autism. The American Academy of Pediatrics has compiled a comprehensive list of this research.
Differences in brain biology
How do these genetic and non-genetic influences lead to autism? Most seem to affect crucial aspects of early brain development. Some seem to affect the way the brain's nerve cells, or neurons, communicate with each other. Others seem to affect the way entire regions of the brain communicate with each other. Research continues to explore these differences with a view to developing treatments and supports that can improve quality of life.
