Objective: Since the diagnosis of delayed-onset posttraumatic stress disorder (PTSD) was introduced in DSM-III, there has been controversy over its prevalence and even its existence. The authors sought to resolve discrepant findings concerning the prevalence of delayed-onset PTSD by conducting a systematic review of the evidence.
Method: A literature search was conducted for case reports and group studies with adequate measurement of delayed-onset PTSD according to DSM criteria. Studies that met inclusion criteria were examined for the defined length of delay for delayed-onset PTSD, presence of symptoms before full diagnostic criteria were met, length of follow-up, prevalence estimates, and other variables. Studies were also examined for differences between immediate-onset PTSD, delayed-onset PTSD, and no-PTSD cases.
Results: Ten case studies and 19 group studies met criteria for inclusion in the review. Studies consistently showed that delayed-onset PTSD in the absence of any prior symptoms was rare, whereas delayed onsets that represented exacerbations or reactivations of prior symptoms accounted on average for 38.2% and 15.3%, respectively, of military and civilian cases of PTSD.
Conclusions: The discrepant findings in the literature concerning prevalence can be largely, but not completely, explained as being due to definitional issues. Little is known about what distinguishes the delayed-onset and immediate-onset forms of the disorder. Continuing scientific study of delayed-onset PTSD would benefit if future editions of DSM were to adopt a definition that explicitly accepts the likelihood of at least some prior symptoms.