title: Emotional reactivity to a single inhalation of 35% carbon dioxide and its association with later symptoms of posttraumatic stress disorder and anxiety in soldiers deployed to Iraq.
abstract: BACKGROUND
  The identification of modifiable predeployment vulnerability factors that increase the risk of combat stress reactions among soldiers once deployed to a war zone offers significant potential for the prevention of posttraumatic stress disorder (PTSD) and other combat-related stress disorders. Adults with anxiety disorders display heightened emotional reactivity to a single inhalation of 35% carbon dioxide (CO(2)); however, data investigating prospective linkages between emotional reactivity to CO(2) and susceptibility to war-zone stress reactions are lacking.
  
  
  OBJECTIVE
  To investigate the association of soldiers' predeployment emotional reactivity to 35% CO(2) challenge with several indices of subsequent war-zone stress symptoms assessed monthly while deployed in Iraq.
  
  
  METHODS
  Prospective cohort study of 158 soldiers with no history of deployment to a war zone were recruited from the Texas Combat Stress Risk Study between April 2, 2007, and August 28, 2009.
  
  
  METHODS
  Multilevel regression models were used to investigate the association between emotional reactivity to 35% CO(2) challenge (assessed before deployment) and soldiers' reported symptoms of general anxiety/stress, PTSD, and depression while deployed to Iraq.
  
  
  RESULTS
  Growth curves of PTSD, depression, and general anxiety/stress symptoms showed a significant curvilinear relationship during the 16-month deployment period. War-zone stressors reported in theater were associated with symptoms of general anxiety/stress, PTSD, and depression. Consistent with the prediction, soldiers' emotional reactivity to a single inhalation of 35% CO(2)-enriched air before deployment significantly potentiated the effects of war-zone stressors on the subsequent development of PTSD symptoms and general anxiety/stress symptoms but not on the development of depression, even after accounting for the effects of trait anxiety and the presence of past or current Axis I mental disorders.
  
  
  CONCLUSIONS
  Soldiers' emotional reactivity to a 35% CO(2) challenge may serve as a vulnerability factor for increasing soldiers' risk for PTSD and general anxiety/stress symptoms in response to war-zone stressors.
authors.affiliation: Department of Psychology, The University of Texas at Austin, 78712, USA. Telch@austin.utexas.edu
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Telch
authors.forename: David
authors.initials: D
authors.lastname: Rosenfield
authors.forename: Han-Joo
authors.initials: HJ
authors.lastname: Lee
authors.forename: Anushka
authors.initials: A
authors.lastname: Pai
mesh_terms: D000280:Administration, Inhalation; D000293:Adolescent; D000328:Adult; D001008:Anxiety Disorders / Q000175:diagnosis* / Q000523:psychology*; D001143:Arousal; D002245:Carbon Dioxide; D003130:Combat Disorders / Q000175:diagnosis* / Q000523:psychology*; D003866:Depressive Disorder / Q000175:diagnosis / Q000523:psychology; D004644:Emotions; D005260:Female; D006801:Humans; D054542:Iraq War, 2003-2011; D008297:Male; D008889:Military Personnel / Q000523:psychology*; D011446:Prospective Studies; D018570:Risk Assessment; D013313:Stress Disorders, Post-Traumatic / Q000175:diagnosis* / Q000523:psychology*; D013781:Texas; D055815:Young Adult
chemical_list: D002245:Carbon Dioxide