High burden of subthreshold DSM‐5 post‐traumatic stress disorder in U.S. military veterans

A substantial proportion of individuals worldwide develop post‐traumatic stress disorder (PTSD) following exposure to traumatic events1, 2, 3. Although the epidemiology of PTSD has been widely studied1, 2, 3, fewer studies have examined subthreshold PTSD, defined as experiencing clinically significant symptoms of PTSD but not meeting full diagnostic criteria for the disorder. With the field of psychiatry increasingly moving towards a dimensional perspective of mental disorders, it is important to understand the burden of subthreshold manifestations of these disorders.

The lifetime prevalence of subthreshold PTSD has ranged from 3.6 to 25.6%2, 4, 5, 6. While not a formal diagnosis, subthreshold PTSD is associated with elevated rates of comorbid psychiatric disorders, suicidality, and physical health problems compared to trauma‐exposed individuals without subthreshold or threshold PTSD2, 4, 5, 6. To date, however, only two studies have examined the epidemiology of subthreshold PTSD as defined using the DSM‐5. The first analyzed data from the World Health Organization World Mental Health Surveys and found that the prevalence of subthreshold PTSD ranged from 0.7 to 4.6%, depending on the definition used. Further, individuals with subthreshold PTSD were 2.5‐5 times more likely to have a comorbid mood or anxiety disorder compared to trauma‐exposed controls7. This study was limited by the operationalization of PTSD, which was derived from a DSM‐IV module and did not include the new DSM‐5 symptoms. The second study of a national sample of Vietnam veterans found that the prevalence of current subthreshold PTSD ranged from 1.9 to 5.7%, and that the comorbidity between DSM‐5 subthreshold PTSD and comorbid disorders ranged from 0.7 to 30.9%8. While these studies provide important insight into the prevalence and correlates of subthreshold DSM‐5 PTSD, additional population‐based data are needed to better understand the burden of this condition.

We analyzed data from the National Health and Resilience in Veterans Study (NHRVS), a contemporary, nationally representative cohort of U.S. military veterans, to examine the prevalence and clinical correlates of DSM‐5 subthreshold PTSD. The NHRVS, conducted in 2013, surveyed 1,484 veterans aged 20+. The sample was ascertained from KnowledgePanel, a nationally representative survey research panel representing approximately 98% of U.S. households. Post‐stratification weights were applied to permit generalizability of results to the U.S. veteran population. Study constructs were assessed with the following tools: Trauma History Screen, PTSD Checklist for DSM‐5 (PCL‐5)9, Mini International Neuropsychiatric Interview and Patient Health Questionnaire‐4 for lifetime and current psychopathology, respectively, Fagerström Test for Nicotine Dependence, and Short Form‐8 (SF‐8) Health Survey for mental and physical functioning10.

Lifetime PCL‐5 responses were used to create a three‐group variable: a) no/low PTSD symptoms (defined as endorsement of ≤1 PTSD criteria B‐E at a severity of “moderate” or higher); b) subthreshold DSM‐5 PTSD (defined as endorsement of 2 or 3 B‐E criteria, or all 4 B‐E criteria but not 1 month symptom duration and/or functional impairment); and c) probable lifetime DSM‐5 PTSD (defined as meeting criteria A‐G for PTSD). A comparable three‐level variable was created for past‐month PTSD symptoms, with a score ≥38 on the PCL‐5 distinguishing between subthreshold and probable PTSD in the absence of past‐month symptom duration and functional impairment assessment in the NHRVS. Weighted prevalence of lifetime and past‐month subthreshold DSM‐5 PTSD was computed in the full sample (N=1,478; 6 subjects had missing data). Other analyses were conducted in only trauma‐exposed veterans (N=1,268). Logistic regression and multivariable analyses of covariance were conducted to examine associations of probable and subthreshold PTSD with comorbid psychiatric disorders and SF‐8 scores. Analyses were adjusted for socio‐demographic variables, combat veteran status, number of lifetime traumas, and any lifetime mental disorder.

The lifetime and past‐month prevalence of subthreshold PTSD was 22.1% and 13.5%, respectively, and higher than the prevalence of lifetime (8.0%) and past‐month (4.5%) probable PTSD. The prevalence of lifetime subthreshold PTSD was higher in women than in men (30.3% vs. 21.2%, X²=10.3, p=0.006) and, although the prevalence of lifetime probable PTSD decreased across age groups (20.8% in 18‐34 year olds to 1.9% in 75+ year olds), the prevalence of subthreshold PTSD remained relatively stable across all but the 75+ age group (21.1% to 26.6%).

Lifetime subthreshold PTSD was associated with a greater likelihood of all lifetime (i.e., major depressive, social anxiety, alcohol and drug use disorders) and current (i.e., major depressive and generalized anxiety disorders, suicidal ideation) psychiatric outcomes, except nicotine dependence, relative to veterans reporting no/low symptoms (adjusted odds ratio, AOR range from 1.7 for lifetime alcohol use disorder to 4.9 for current generalized anxiety disorder). Veterans with probable PTSD had a greater likelihood of all outcomes relative to veterans with no/low symptoms, and these associations were numerically larger in magnitude relative to the subthreshold PTSD group (AOR range from 1.9 for lifetime nicotine dependence to 19.3 for current generalized anxiety disorder). Although individuals with probable PTSD reported the poorest functioning (d range from 0.31 for health rating to 1.45 for mental health), veterans with subthreshold PTSD also reported significantly worse functioning than veterans with no/low PTSD symptoms on all SF‐8 measures (d range from 0.12 for health rating to 0.41 for mental health and social functioning). A similar pattern of findings was observed in analyses of past‐month subthreshold and probable PTSD.

The results of this study suggest that a strikingly high proportion of U.S. veterans – approximately one in three – experience clinically significant PTSD symptoms in their lifetime. They further suggest that subthreshold PTSD is associated with an elevated burden of comorbid psychiatric disorders, as well as decrements in mental and physical functioning. While the field has not reached a consensus regarding the operationalization of subthreshold PTSD, these results underscore the importance of assessment, prevention and treatment efforts in targeting veterans and other trauma‐affected individuals with PTSD symptoms below the diagnostic threshold.

Natalie P. Mota1, Jack Tsai2,3, Jitender Sareen4, Brian P. Marx5, Blair E. Wisco6, Ilan Harpaz‐Rotem3,7, Steven M. Southwick3,7, John H. Krystal3,7, Robert H. Pietrzak3,7
1Department of Clinical Health Psychology, University of Manitoba, Winnipeg, Canada; 2U.S. Department of Veterans Affairs, New England Mental Illness Research, Education, and Clinical Center, West Haven, CT, USA; 3Department of Psychiatry, Yale University School of Medicine, New Haven, CT, USA; 4Departments of Psychiatry, Psychology, and Community Health Sciences, University of Manitoba, Winnipeg, Canada; 5U.S. Department of Veterans Affairs National Center for Posttraumatic Stress Disorder, VA Boston Healthcare System, and Division of Psychiatry, Boston University School of Medicine, Boston, MA, USA; 6Department of Psychology, University of North Carolina at Greensboro, Greensboro, NC, USA; 7U.S. Department of Veterans Affairs National Center for Posttraumatic Stress Disorder, VA Connecticut Healthcare System, West Haven, CT, USA

The National Health and Resilience in Veterans Study was supported by the U.S. Department of Veterans Affairs National Center for Posttraumatic Stress Disorder and a private donation.