Correlation between anxiety disorders and PTSD The mega study on the genetic correlations of psychiatric (and neurological) disorders published in Science this summer has one interesting non-correlation: between anxiety disorders and PTSD.



Are the two (anxiety disorders and PTSD) correlated epidemiologically though? If so, is there a good explanation for the lack of genetic correlation?
TLDR

The DSM-5 recognises the epidemiology of anxiety within PTSD, and the reason for the lack of genetic correlation is the fact that in PTSD, the anxiety is exogenous (environmental) rather than endogenous (biological via genes or other means).

The debate

The DSM-5, is the current version of the Diagnostic and Statistical Manual of Mental Disorders written by the American Psychiatric Association (APA, 2013).

As highlighted by Fizz,


  surprisingly, it looks like [the classification of PTSD] is not just a naming issue. It looks like there was a big brouhaha about moving PTSD out of anxiety disorders in DSM-5 (Pai, Suris, &amp; North 2017).


Changes to the diagnostic criteria from the DSM-IV to DSM-5 include:


the relocation of PTSD from the anxiety disorders category to a new diagnostic category named “Trauma and Stressor-related Disorders”,
the elimination of the subjective component to the definition of trauma,
the clarification and tightening of the definitions of trauma and exposure to it,
the increase and rearrangement of the symptoms criteria, and
changes in additional criteria and specifiers.


Some people even question the validity of such a diagnosis (Summerfield, 2001).


  Summary points
  
  
  A psychiatric diagnosis is not necessarily a disease
  Distress or suffering is not psychopathology
  Post-traumatic stress disorder is an entity constructed as much from sociopolitical ideas as from psychiatric ones
  The increase in the diagnosis of post-traumatic stress disorder in society is linked to changes in the relation between individual “personhood” and modern life
  


An editorial in the American Journal of Psychiatry commented that it was rare to find a psychiatric diagnosis that anyone liked to have but post-traumatic stress disorder was one (Andreasen, 1995).

The History

War Cowardice

In World War One, the executions of 306 British and Commonwealth soldiers took place (Trueman, 2015; Taylor-Whiffen, 2011). Such executions, for crimes such as desertion and cowardice, remain a source of controversy with some believing that many of those executed should be pardoned as they were suffering from what later called shell shock, even during World War 2.


  Between 1914 and 1918, the British Army identified 80,000 men with what would now be defined as the symptoms of shellshock. There were those who suffered from severe shell shock. They could not stand the thought of being on the front line any longer and deserted. Once caught, they received a court martial and, if sentenced to death, shot by a twelve man firing squad. (Trueman, 2015)


Shell Shock


  Shell shock - now called post-traumatic stress disorder - was first recognised in print by Dr Charles Myers of the British Psychological Society in 1915. By the end of the war the army had dealt with more than 80,000 cases. (Taylor-Whiffen, 2011)


Britain was not alone in executing its own soldiers. The French are thought to have killed about 600. The Germans, whose troops outnumbered the British by two to one, shot 48 of their own men, and the Belgians 13. In 2001, 23 executed Canadians were posthumously honoured by their government, and five troops killed by New Zealand's military command also recently won a pardon. Not one American or Australian soldier was executed, but the Americans often used humiliation as a punishment for desertion.

PTSD

The US National Center for PTSD covers the start of PTSD being a diagnosis within the DSM.


  The risk of exposure to trauma has been a part of the human condition since we evolved as a species. Attacks by saber tooth tigers or twenty-first century terrorists have probably produced similar psychological sequelae in the survivors of such violence. Shakespeare's Henry IV appears to meet many, if not all, of the diagnostic criteria for Posttraumatic Stress Disorder (PTSD), as have other heroes and heroines throughout the world's literature. The history of the development of the PTSD concept is described by Trimble (1985).
  
  In 1980, the American Psychiatric Association (APA) added PTSD to the third edition of its Diagnostic and Statistical Manual of Mental Disorders (DSM-III) nosologic classification scheme (APA, 1980). Although controversial when first introduced, the PTSD diagnosis has filled an important gap in psychiatric theory and practice. From an historical perspective, the significant change ushered in by the PTSD concept was the stipulation that the etiological agent was outside the individual (i.e., a traumatic event) rather than an inherent individual weakness (i.e., a traumatic neurosis). The key to understanding the scientific basis and clinical expression of PTSD is the concept of "trauma".


DSM-III

Page 236 states


  Post-traumatic Stress Disorder, Chronic or Delayed
  The essential feature is the development of characteristic symptoms following a psychologically traumatic event that is generally outside the range of usual human experience.
  
  The characteristic symptoms involve reexperiencing the traumatic event; numbing of responsiveness to, or reduced involvement with, the external world; and a variety of autonomic, dysphoric, or cognitive symptoms.
  The stressor producing this syndrome would evoke significant symptoms of distress in most people, and is generally outside the range of such common experiences as simple bereavement, chronic illness, business losses, or marital conflict. The trauma may be experienced alone (rape or assault) or in the company of groups of people (military combat). Stressors producing this disorder include natural disasters (floods, earthquakes), accidental man-made disasters (car accidents with serious physical injury, airplane crashes, large fires), or deliberate man-made disasters (bombing, torture, death camps). Some stressors frequently produce the disorder (e.g., torture) and others produce it only occasionally (e.g., car accidents). Frequently there is a concomitant physical component to the trauma which may even involve direct damage to the central nervous system (e.g., malnutrition, head trauma). The disorder is apparently more severe and longer lasting when the stressor is of human design. The severity of the stressor should be recorded and the specific stressor may be noted on Axis IV (p. 26).


The current (DSM-5) definition of PTSD (under Specific Phobia: Differential Diagnosis within the Anxiety section of DSM-5)


  If the phobia develops following a traumatic event, posttraumatic stress disorder (PTSD) should be considered as a diagnosis. However, traumatic events can precede the onset of PTSD and specific phobia. In this case, a diagnosis of specific phobia would be assigned only if all of the criteria for PTSD are not met (APA, 2013 p.202)


Trauma- and stressor-related disorders include


  disorders in which exposure to a traumatic or stressful event is listed explicitly as a diagnostic criterion. These include reactive attachment disorder, disinhibited social engagement disorder, posttraumatic stress disorder (PTSD), acute stress disorder, and adjustment disorders. Placement of this chapter reflects the close relationship between these diagnoses and disorders in the surrounding chapters on anxiety disorders, obsessive-compulsive and related disorders, and dissociative disorders. (APA, 2013 p.265)


Psychological distress following exposure to a traumatic or stressful event is quite variable.


  In some cases, symptoms can be well understood within an anxiety- or fear-based context. It is clear, however, that many individuals who have been exposed to a traumatic or stressful event exhibit a phenotype in which, rather than anxiety- or fear-based symptoms, the most prominent clinical characteristics are anhedonic and dysphoric symptoms, externalizing angry and aggressive symptoms, or dissociative symptoms. Because of these variable expressions of clinical distress following exposure to catastrophic or aversive events, the aforementioned disorders have been grouped under a separate category: trauma- and stressor-related disorders.


See also: DSM-5 info. sheet on PTSD (Free PDF)

So, to your question

Are the two (anxiety disorders and PTSD) correlated epidemiologically? If so, is there a good explanation for the lack of genetic correlation?

DSM-5 recognises the epidemiology of anxiety within PTSD, and the reason for the lack of genetic correlation is the fact that in PTSD, the anxiety is exogenous (environmental) rather than endogenous (biological via genes or other means).

References

Andreasen, N. C. (1995). Posttraumatic stress disorder: psychology, biology, and the manichaean warfare between false dichotomies. The American journal of psychiatry, 152(7), 963–965. https://doi.org/10.1176/ajp.152.7.963

APA (1980). Diagnostic and statistical manual of mental disorders, (3rd ed.). Washington, DC: American Psychiatric Publishing.

APA (2013). Diagnostic and Statistical Manual of Mental Disorders, (5th ed.). Washington, DC: American Psychiatric Publishing.

Pai, A., Suris, A. M., &amp; North, C. S. (2017). Posttraumatic Stress Disorder in the DSM-5: Controversy, Change, and Conceptual Considerations. Behavioral Science, 7(1), 7. https://doi.org/10.3390/bs7010007

Summerfield, D. (2001). The invention of post-traumatic stress disorder and the social usefulness of a psychiatric category. BMJ : British Medical Journal, 322(7278), 95–98. https://doi.org/10.1136/bmj.322.7278.95

Taylor-Whiffen, P. (2011) Shot at Dawn: Cowards, Traitors or Victims? BBC History [Online] Retrieved from: http://www.bbc.co.uk/history/british/britain_wwone/shot_at_dawn_01.shtml

Trimble, M. D. (1985). Post-traumatic Stress Disorder: History of a concept. In C.R. Figley (Ed.), Trauma and its wake: The study and treatment of Post-Traumatic Stress Disorder. New York: Brunner/Mazel.

Trueman, C. N. (2015). World War One executions. The History Learning Site [Online] Retrieved from: https://www.historylearningsite.co.uk/world-war-one/the-western-front-in-world-war-one/world-war-one-executions/