Biology of ASD

Autism Spectrum Disorder

• Autism is defined as a neurobehavioral condition marked by impairments in social interactions functional communications, and repetitive behaviors manifesting in early childhood  

• Typically diagnosed age 2-5 

• A spectral disorder because it is actually a large number of slightly different conditions with different manifestations across the behavioral ranges 

• Half of people with ASD demonstrate above average cognition 

ASD & Vaccines

Vaccines do not cause ASD 

• Incorrect belief based on Lancet paper in 1977 that examined 12 children 

• Paper was later retracted when it was found that the main author Andrew Wakefield had falsified some of the data 

• Wakefield had his license to practice medicine revoked 

• Many studies which combine to include over 1.5 million children have found no link between vaccination, vaccination schedule, or vaccine additives and ASD 

Savantism

the possession of profound mental or intellectual abilities well beyond what is considered normal 

• While the two may coexist in one person, they are independent aspects of that person 

• Rain Man skewed the perception by showing a character who was a math savant with ASD 

Introversion

is the preference to avoid groups and to prefer time alone 

• Very strong evidence of genetic basis of introversion 

• D4DR gene encodes a dopamine receptor 

• Introverts have increased sensitivity to stimulation by environmental factors like noise and social interactions 

• Introverts find interactions exhausting and recharge with alone time 

• Extroverts use interactions to recharge 

Frequency of ASD

• CDC estimates 1 in 68 children in the US have ASD 

• 1 in 42 boys 

• 1 in 189 girls 

Some people claim this is on a dramatic rise 

• Improvements in diagnostic tools and support are responsible for shift from undiagnosed to diagnosed 

• Large studies of adults in US and UK show that frequency in adult population is similar to that in children 

• Poor diagnosis missed, any of these people as children 

Timing of Development of ASD 

• Behavior leading to diagnosis typically occurs between ages 2-5 

• 2014 paper showed neuroimages of developing fetal brains 

• Significant differences in neuropatterans between neurotypical and children who developed ASD 

• Changes occur before birth not due to exposures after birth 

Why is ASD more common in boys?

X Chromosome linked 

• Multiple loci on X Chromosome have been identified 

Chromatin restructuring 

• One candidate gene is involved in chromatin restructuring on the X chromosome 

Females have defenses against ASD 

• With inverted repeats it takes many more repeats for ASD to manifest in females than in males 

Risk Factors: Paternal Factors

• Dad accumulates point mutations and variable repeats in his germ cells as he ages 

• Risk increases as dad ages 

Risk Factors: Maternal Factors

• Inflammation during pregnancy 

• Lupus and serious viral infections have been connected to ASD 

• Anti-depressant Drugs in first trimesters 

• Other external factors probably involved as well