This week’s article discussed a hypothesis surrounding the environmental and genetic factors that may contribute to the development of autism. From 1970 to 2002, the diagnosed cases of autism rose from 3 in 1000 to 66 in 1000, increasing over twenty fold. Naturally, a lot of research has gone into why these rates seem to be increasing so dramatically. To understand this, we need to understand what can potentially cause autism.
Neurological diseases or disorders are complex, and focusing in on a single neurological dysfunction is rarely possible. The complexity of our human brain often leads to multiple hypotheses on what causes each disease. While genetic factors play a role, there are environmental factors that can cause autism as well. While multiple theories for the causes of autism exist, our paper this week focused on the role of heavy metal toxicity and oxidative stress in facilitating its development. Heavy metals, such as cadmium, arsenic, lead, and mercury, can have profound effects on the brain even at small concentrations, being correlated with disorders like ADHD and autism, and even diseases like Parkinson’s and Alzheimer’s.
Heavy metal compounds can be referred to as xenobiotics, chemicals found in our body that are not produced or expected to be present in our biological system. Heavy metals can bind strongly to sulfur containing compounds in our bodies, disrupting normal paths of sulfur metabolism. Sulfur, through glutathione, methionine, and other molecules, plays an integral role in DNA methylation, which is important in gene regulation and other processes. Particularly, this metabolism is crucial during oxidative stress, thus metal’s interfering with this pathway can lead to general dysfunction, leading to symptoms that often characterize autism. For example, the body attempts to clear xenobiotics from the body by binding them to glutathione and clearing them in urine. Therefore, heavy metals can remove important sulfur-containing compounds from our bodies, leaving us more vulnerable to oxidative stress.
Can the actions of heavy metals explain the surge in cases of documented autism? If this was the case, we would have to expect rising levels of heavy metals being inadvertently consumed/entering the body. A well-known controversy surrounding heavy metals involved thiomersal, an ethylmercury-based preservative used to prevent bacterial infections, found in vaccines. Rising awareness of the deleterious effects of mercury in the 1970’s led to a well-publicized, fierce backlash against the vaccine. Despite extensive research among scientists declaring the concentrations of mercury in these vaccines were far below toxic levels, controversy still surrounds the compound, and it has been removed completely from vaccines. Its removal did not decrease the rising autism rates, reliably indicating it wasn’t a significant cause of autism. In addition, heavy metals are sometimes present in soil, while trace amounts of heavy metals can be found in certain cosmetics. These levels aren’t in themselves very dangerous, but regular usage is hypothesized to have possible side effects. Despite our possible exposure to heavy metals, little is known about whether exposure is increasing. In fact, increased awareness of the toxic effects of heavy metals has led to government agencies cutting back their usage. Thus, it is possible heavy metal exposure may even be decreasing, despite autism levels still rising.
What else could cause autism? A less chemical explanation is lack of proper social interaction. Studies have shown that babies who didn’t receive much touch from their parents or didn’t receive much attention in early childhood were at a greater risk for developing autism. In a society where it is becoming more likely for both parents to have jobs, it is possible children on average are receiving far less attention from their parents than children raised forty, or even ten years ago. This lack of social interaction could lend itself to the social problems that are displayed by autistic children. However, children who may not see their parents as often still may get plenty of social interaction at their daycare or school. Thus, it is possible this phenomenon isn’t a significant contributor. Because it is hard, even impossible, to provide reliable quantifiable data of this effect, it isn’t easy to cite this as a main cause of the surfacing epidemic.
It is possible that as scientists we are missing a universal factor lending itself to increasing levels of autism. Most likely, it is a random combination of factors leading to each autistic case. However, is it possible that cases of autism aren’t actually increasing? Awareness of autism is constantly increasing, which could lend heavily to the increased amount of documented cases. Cases that may have previously gone unnoticed forty years ago may be diagnosed readily in the current climate. Perhaps the “increasing levels” of autism is actually a marker of a good thing: children with autism being diagnosed more readily may receive positive treatment whereas a child in their same position decades ago may have gone unnoticed, which provides them a better chance to live normal, successful lives.
Most neurological disorders are as complicated as they are devastating. The etiology of current disorders like autism are often filled with hazy areas and judgment calls. While it may be difficult in the short run to develop a universal “cure” for autism or similar disorders, increasing awareness can help provide treatment for those in need. However, there is a fine line between increased awareness and trigger-happy diagnoses. Diagnosis with social disorder often comes with a stigma that may make the patients feel even more helpless. As we seek to find the scientific explanations of these disorders, it is important for us to treat each case with care and deliberation.
Is Autism really on the rise?
