Abstract

The Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5) (American Psychiatric Association 2013a) was a major revision of the DSM-IV-TR (1994). Despite numerous critiques of the DSM-5, none have analyzed statistically the actual diagnostic structure of the DSM-5 itself. That is particularly the case regarding the diagnosis of Posttraumatic Stress Disorder (PTSD), a diagnosis which has attracted international attention since the Afghanistan and Iraq wars, and which has been extensively investigated and profoundly affected by DSM-5 changes. The present study used a metatheory and content analysis approach to conceptually differentiate the Trauma-Related and Stressor-Related Disorders in the DSM-5, the diagnostic class of disorders which includes PTSD. A common Symptom Requirement Dichotomy (i.e., Mandatory versus Not Mandatory) was indicated and found to statistically differentiate the Trauma-Related and Stressor-Related Disorders in the DSM-5. That same Symptom Requirement Dichotomy was then used to conceptually and statistically differentiate Adult and Child DSM-5 disorders previously reported for the DSM-5 Field Trials (Regier et al. 2013). DSM-5 Field Trial Site Kappa Reliability Coefficients for both Adult and Child disorders were found to be a quadratic function of the “Number of Not Mandatory” symptoms in the DSM-5, an a priori feature of the diagnostic structure or coding system of the DSM-5 that preempts both clinical assessment and diagnosis. Implications of systematic error in the DSM-5 and real world outcomes were discussed, limitations of the present study were addressed, and recommendations for developing an alternative classification system of mental disorders were proffered.