GENETIC
A definite neural basis exists which causes adult Attention Deficit Hyperactivity Disorder (ADHD). Genetics plays a huge role in determining who will have ADHD, and who will not. For instance, in identical twins, it is 66% likely that if one twin has ADHD, the other twin also will; where-as for fraternal twins, the percentage decreases to 28%.
In reviewing items which are attributed to heredity the following behaviors are interesting to note: The heritability estimate for ADHD is higher than for schizophrenia, depression/mood disorders, or intelligence. Indeed, ADHD’s heritability estimate is almost the same as for height.
The genes involved seem to be ones which impact on dopamine and serotonin transmission; especially dopamine and nor-epinephrine. Both of these neuro-chemicals are critical for prefrontal cortex (PFC) function.
The Pre-frontal Cortex controls such functions as:
• Attention,
• Working memory, and
• Impulse control
Imaging studies show decreased activity of both dopamine and nor-epinephrine in the prefrontal lobe; but increase activity in the striatum (which means that these neuro-chemicals are trying as best they can to compensate for the decreased absorption in the PFC.
Plasma and urine metabolites of nor-epinephrine are significantly lower with children and adults with ADHD. Interestingly, nor-epinephrine is involved in both the distractibility and hyperactivity component of ADHD.
Patients with ADHD fail to utilize normal neural pathways to process information. The anterior cingulated is used normally, but not in ADHD. Instead of a small, circumscribe area being used to make determinations about logical sequences, the brain uses two, and sometimes three other larger areas to compensate for the area they are not using.
ENVIRONMENTAL RISK FACTORS
Although ADHD is a genetic disease, environmental risk factors play a role in exacerbating this disorder.
Biological
• Dietary studies were all negative (including the effect of sugar on hyperactivity).
• Lead exposure may play a role.
• Pregnancy and/or delivery complications may play a role.
• Premature or low birth weight infants impacts on ADHD.
• Maternal smoking may have some affect on ADHD.
Psycho-Social
Discord or chaos within the family may exacerbate a pre-disposition for ADHD.
Psychiatric and Mental Health Congress, 2006
Http://viss.cmellc.com/psychcongress/
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