Comorbidity of Psychiatric Disorders and Posttraumatic Stress Disorder

Posttraumatic stress disorder (PTSD) commonly co-occurs with other psychiatric disorders. Data fromepidemiologic surveys indicate that the vast majority of individuals with PTSD meet criteria for at least oneother psychiatric disorder, and a substantial percentage have 3 or more other psychiatric diagnoses. A numberof different hypothetical constructs have been posited to explain this high comorbidity; for example, theself-medication hypothesis has often been applied to understand the relationship between PTSD and substanceuse disorders. There is a substantial amount of symptom overlap between PTSD and a number ofother psychiatric diagnoses, particularly major depressive disorder. It has been suggested that high rates ofcomorbidity may be simply an epiphenomenon of the diagnostic criteria used. In any case, this high degreeof symptom overlap can contribute to diagnostic confusion and, in particular, to the underdiagnosis of PTSDwhen trauma histories are not specifically obtained. The most common comorbid diagnoses are depressivedisorders, substance use disorders, and other anxiety disorders. The comorbidity of PTSD and depressivedisorders is of particular interest. Across a number of studies, these are the disorders most likely to co-occurwith PTSD. It is also clear that depressive disorder can be a common and independent sequela of exposure totrauma and having a previous depressive disorder is a risk factor for the development of PTSD once exposureto a trauma occurs. The comorbidity of PTSD with substance use disorders is complex because while asubstance use disorder may often develop as an attempt to self-medicate the painful symptoms of PTSD,withdrawal states exaggerate these symptoms. Appropriate treatment of PTSD in substance abusers is a controversialissue because of the belief that addressing issues related to the trauma in early recovery can precipitaterelapse. In conclusion, comorbidity in PTSD is the rule rather than the exception. This area warrantsmuch further study since comorbid conditions may provide a rationale for the subtyping of individuals withPTSD to optimize treatment outcomes.