Strengths

• Modern research has allowed us to actually locate the genetic variations using very large sample sizes.
• Modern research recognizes the interaction of environmental and biological factors.
• There is animal research that supports the theories. This research is experimental, allowing us to cautiously infer a cause and effect relationship between independent and dependent variables.

Limitations

• Correlational research means that causation cannot be established and bidirectional ambiguity cannot be resolved.
• Twin studies have not been highly reliable in their results.
• In twin studies there is a problem with population validity - samples are so small that there is difficulty in generalizing results. In addition, the life of a twin may be different from the experience of the general population.
• In cases of PTSD, it is difficult to find twins who have experienced the same level of trauma. Although they may have both been in the Vietnam war, they had different experiences; even though both lost their mother in a tragic accident, one may have been more attached to the parent than the other.
• The explanation does not account for the variations in the symptomology of PTSD. For example, why was "Shell Shock" the common form of PTSD after World War I? Why do we not see those symptoms today?
• It is not yet clear how the genetic variations that have been discovered interact to produce PTSD.
• A lot of research has been done on animals. This is problematic because we have to assume that what is determined to be PTSD in animals can be generalized to the human experience.
• More prospective studies need to be done to determine the validity of the theories. Otherwise, we cannot be sure if the levels of neurochemicals are the cause or the effect of PTSD.