As with the previous installments, we will quickly see that much
research remains to be done before the overarching biological
basis of PTSD is fully characterized. There may even be some
epigenetic influences to consider. To begin examining these
genetic issues, I will discuss research on variable responses to
stress in outbred laboratory animals and then move on to genetic
and environmental influences in humans. Hints of genes One of
the most difficult challenges facing researchers interested in
the biological explanation of PTSD lies in the extraordinary
variability of stress responses. Can the disorder be explained
genetically? Environmentally? It is in many ways the age-old
question of nature versus nurture, without the convenient
rejoinder that it is "both." The strongest hint that PTSD
variability may be explained as a preexisting condition rose
from the twin studies discussed in Part 2.2 Researchers found an
increased prevalence of PTSD in monozygotic twins who were
discordant when exposed to intensel