Dead inside: A Systematic Review of the Psychosocial Effects of Combat-Related Emotional Numbing

Background and Purpose:  In the Diagnostic and Statistical Manual of Mental Disorders (5th ed.; American Psychiatric Association, 2013) posttraumatic stress disorder (PTSD) symptoms of emotional numbing (EN) include markedly diminished interest in significant activities, feelings of detachment or estrangement, and blunted positive affect, despite an intact ability to access negative emotional states.  Of the PTSD symptoms, the EN cluster is associated with especially poor psychosocial outcomes for combat veterans, including suicide (Kerig et al., 2016).  The two-fold purpose of this review was to systematically examine the recent published evidence on the psychosocial effects of EN in combat veterans compared to other PTSD symptom clusters, and to investigate emerging evidence of the differential impact by race/ethnicity and gender.  

Methods:  This review was conducted using procedures outlined by Littell, Corcoran, and Pillai (2008) and the PRISMA guidelines.  It covered the period from January 2012 to January 2017 and updated a previous narrative review more limited in scope (Hassija, Jakupcak, & Gray, 2012).  Studies were identified by inputting targeted search terms into nine databases (PubMed, PsycINFO, PILOTS, Clinicaltrials.gov, Web of Knowledge, CINAHL, Cochrane Reviews, Social Work Abstracts, and Google Scholar), hand-searching relevant reference lists, and using a customized Google search to identify grey literature.  Two trained reviewers independently applied prespecified criteria for rigor, and a third adjudicated inconsistencies.  Risk of bias was independently assessed using the 14-item National Institutes of Health (NIH) Quality Assessment Tool for Observational Cohort and Cross-sectional Studies (NIH, 2014). 

Results:  The reviewers identified 19 studies for inclusion and assessed most studies as having a fair risk of bias.  Interrater agreement was substantial (k = 0.80).  The total sample included 88,824 combat veterans from different war eras, aged 18-94 (M = 39.01, SD = 8.61), 11.25% women (n = 9,997), and 32.54% non-White (n = 28,912).  All studies were observational.  Most were cross-sectional (n = 15).  Studies varied in how broadly they defined EN.  Most conceptualized PTSD using a popular 4-factor analytic model, though 5- and 6- factor models have demonstrated superior fit.  Just over half (n= 10) relied solely on limited self-report measures to assess PTSD.  Compared to other PTSD symptoms, results showed EN exerted independent and unique psychosocial effects for combat veterans in the following domains: relationship functioning; mental health and negative cognitions; health service utilization; physical and mental health quality of life; substance use disorders; aggression; and suicidality.  Also, EN was shown to affect diverse groups differently, and interactions between gender and culture influenced reporting. 

Conclusions and Implications:  Effectively treating EN could improve critical health- and mental health-related outcomes in combat veterans, yet the psychosocial impact of EN is understudied.  Longitudinal studies and randomized controlled trials are needed to better understand the association between EN and adverse psychosocial outcomes, particularly in women and non-White veterans.  Future studies should operationalize EN using models that show superior fit with nationally representative veteran samples, and combine diagnostic and self-report measures with collateral data.  Further exploration of EN and suicidality in the veteran population is of chief importance.