Autism spectrum disorder is the term used to describe a range of neurodevelopmental disorders characterized by communication difficulties, social impairments, and repetitive, restricted, and stereotyped behavior. The U.S. autism rate is currently 1 in 68, though it remains to be determined whether this is due to an increase in prevalence or diagnosis. The severity of autism can range from a milder form, Asperger syndrome, to the most severe form, autistic disorder. Most cases are identified before the age of 3. Hallmark features in infants are unresponsiveness to people or an intent focus on one item with the exclusion of other items for long periods of time. Children with ASD may fail to respond to their own names and avoid eye contact with other people. Additionally, ASD children engage in repetitive movements such as rocking or self-abusive behavior like head-banging or biting. They have difficulty interpreting the thoughts and feelings of others because they do not understand social cues such as facial expressions or tone of voice. A variety of influential factors contributing to the onset of ASD have been identified, though the exact cause of ASD has yet to be determined.
Autism Diagnosis
Below is a list of indicators used in the diagnostic process of autism. Severe cases of autism are usually diagnosed at a much earlier age than milder cases. Asperger’s syndrome, a mild form of ASD, is typically identified by later indicators. Individuals with Asperger’s have relatively normal intelligence and cognitive ability but impaired social functioning. Diagnosis is completed through a comprehensive evaluation by a team including a psychologist, psychiatrist, neurologist, speech therapist, and other professionals involved in ASD diagnosis.
Early indicators
- no pointing or babbling by age 1
- no response to name
- poor eye contact
- loss of social skills or language
- no single words by 16 months or 2-word phrases by age 2
- no smiling or social responsiveness
- excessive lining up of objects or toys
Later indicators
- impaired ability to initiate/sustain a conversation with others
- impaired or absent imaginative or social play
- impaired ability to make friends with peers
- preoccupation with certain objects or subjects
- repetitive, stereotyped, or unusual language use
- restricted patterns of interest with abnormal focus and intensity
- inflexible adherence to specific rituals or routines
Contributing Factors to ASD Onset
Although genetic factors are involved in ASD onset, they only account for 15% of autism cases. Maternal nutrition, infection during pregnancy, prematurity, and parental age are among the environmental factors implicated in ASD. Immune system abnormalities and zinc deficiency also play a role in altered synaptic transmission present in ASD.
- Fetal brain development failures are connected to an increased autism risk. Infections associated with autism include: prenatal influenza, rubella, and cytomegalovirus infections.
- Zinc Deficiency is present in those with ASD. Zinc is the second most abundant trace element in the body, and is implicated in processes such as cell division and differentiation. A deficiency of zinc causes neuropsychological symptoms, memory and learning impairments, behavioral issues, and enhanced glutamate excitotoxicity. Zinc deficiency is also connected to compromising the immune system, which may be connected to prenatal infection risk.
- Abnormal melatonin synthesis may also be implicated in autism. Melatonin is a neurohormone responsible for regulating circadian rhythms, the body’s internal clock involved in regulating the sleep/wake cycle. Low melatonin levels are observed in individuals with ASD. Children with ASD have sleep abnormalities such as frequent interrupted sleep, reduced duration, and prolonged sleep onset latency. The circadian abnormalities ins ASD may be due to genetic abnormalities related to melatonin synthesis.
- Maternal diabetes is another ASD risk factor. Obesity, diabetes, and hypertension have been found to occur more often in mothers of ASD children. Obesity has the most significant association with ASD risk.
- Prenatal stress may also increase ASD risk. Prenatal exposure to stress hormones or psychological stress has been shown in various studies to result in abnormal infant immune function that persisted to late childhood. A high stress environment during the prenatal period can prolong the activation of the HPA axis, which is involved in the body’s stress response. Prolonged HPA activation lowers the immune system’s ability to fight off infection.
- Prenatal exposure to valproic acid, an anticonvuslant has also been implicated in ASD onset. Valproic acid is a medication used to treat epilepsy and bipolar disorder.
- Increased parental age in both the mother and the father are connected to ASD risk. Paternal age is linked to ASD risk due to a greater number of mutations present in older sperm that can increase ASD risk. Maternal age is connected to ASD risk through increased pregnancy complications and autoimmunity.
Take-Home Message
The extensive list of possible contributing factors and recent statistics regarding autism is daunting, but it is important to note that the presence of one factor does not necessarily guarantee ASD onset. The identified factors are implicated in ASD, but their relationship to one another is not fully understood. One ASD factor that has been affirmatively ruled out is vaccination. This is NOT connected to ASD in any way, though this idea still seems to continue to circulate. The researcher who conducted the vaccination study was stripped of all medical practicing abilities after it was revealed that the study and data were fabricated. Individuals with ASD greatly benefit from treatment such as social skills training, speech therapy, and applied behavioral analysis. Some medications can be used for side effects such as obsessive-compulsive disorder or anxiety, though the presence of these side effects vary from one case to another. Hopefully with continued research, we can identify the link between the contributing factors and perhaps determine the cause of ASD.
For more information on autism: http://www.ninds.nih.gov/disorders/autism/detail_autism.htm
http://www.autismspeaks.org/
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