Autism is a spectral disorder that is becoming commonly diagnosed. In fact, 1 in 68 children are diagnosed as part of the spectrum. This brings up the question whether the criteria for diagnosing are becoming fine-tuned and therefore more accurate or whether people are stretching the diagnosis because parents demand an answer to why their child is “different.” Because it is a spectrum disorder, autism includes a broad range of social, behavioral, and cognitive deficits. From high-functioning cases of individuals with high IQs and low social skills to cases where communication is not possible, there is no one way to define autism.
Just as with all facets of development, there is a balance between genetics and environment that plays into expression of hereditary traits. There are a number of genes that predispose an individual to becoming autistic, but what is most interesting is the role of environmental factors. Since most cases of autism of diagnosed in early childhood, it is possible that fundamental structures in the brain are altered while in utero, but are not noticed until key developmental periods. Parents might see cognitive deficits from delayed speech progression, abnormal social behaviors, repetitive behaviors, etc. The phenotype for autism lies in the neurological changes in the brain which include alteration of important synaptic proteins needed for long term potentiation. In addition, autistic individuals have a smaller amygdala and hippocampus. The amygdala is important for emotions, emotional behaviors, and motivation while the hippocampus is important for long-term memory. This week’s article focused on how prenatal environment affects the neurological development of the autistic brain.
The author suggests two central components to environmental factors are immune system abnormalities and zinc deficiencies. Maternal stress is one contributor to the altered immune system and changes within the brain. Specifically, mothers under stress have high levels of cortisol which cross the placenta and alter the neurological development. The small hippocampus of autistic patients also leads to high cortisol secretion which may also contribute to abnormal growth. Parental age of both the mother and father contributes to the increase the risk for autism in the offspring. Mothers over 30 years old are more likely to have an autoimmune disorder. The antibodies of these mothers may inappropriately target the growing fetus during critical periods of development. Fathers have an increased risk of sperm mutations with age. Lastly, prenatal infections such as influenza may cause inflammation of the brain. The other major factor for autism, zinc deficiency, actually plays into the altered immune system because low levels of zinc promotes inflammation and impairs immune responses. In addition, zinc deficiency causes gastrointestinal abnormalities commonly linked to autism.
There are many hypotheses for how these abnormalities lead to autism. The immune system alters long term potentiation, a mechanism required for learning and memory. In addition, pro-inflammatory cytokines can affect neurotransmitter release and the ability to send neurological signals. The modification of NMDA receptors necessary for excitation of the neuron is another possible mode of action. There are many other mechanisms touched on in the paper, but I focused on the immune system mechanisms.
Many factors increase the risk for autism, but there is not a complete understanding of the mechanism. Does a zinc deficiency cause autism, or is it merely a side effect? More research is required to form the complete picture of the genetic and environmental causes. Autism might be diagnosed more and more because parents want a single answer to certain quirks or abnormalities of their child. However, autism might be expressed to greater degree because of our culture. Our generation starts families later in life to allow time to establish their careers. In addition, our fast-paced society may contribute to the stress of mothers, producing a dangerous environment for a fetus. No longer are people in the dark or misinformed about what causes autism. I think education is the first step in understanding autism spectrum disorder and moving towards a better understanding.
Resources:
http://www.autismspeaks.org/what-autism
Autism: An Environmental Perspective
