Can 'partial' PTSD explain differences in diagnosis of PTSD by questionnaire self-report and interview after head injury?

OBJECTIVE: Can the concept of 'partial' PTSD explain the disparity between the relatively high incidence of PTSD found using self-report questionnaires and the relatively low incidence using structured interview? It was hypothesized that self-report of greater PTSD symptom severity is associated with increased heart rate and movement when responding to questions about the traumatic event, if 'partial' PTSD is an explanation. RESEARCH
DESIGN: A within participants single group design.
METHODS: Twenty-one adults with head injury underwent self-report (Post-traumatic Stress Disorder Scale) and interview (Clinical Assessment of PTSD) assessments of PTSD, the Traumatic Memory Interview, self-report of mood (Hospital Anxiety and Depression Scale) and cognitive assessment (Wechsler Test of Adult Reading, Auditory Verbal Learning Test, Hayling Test, Digit Symbol Test), during which heart rate and motor activity were recorded.
RESULTS: Self-report of greater PTSD symptom severity was not associated with increases in heart rate or movement during questions about the traumatic event. In fact, heart rate decreased from baseline in those with higher self-report scores for PTSD, consistent with curiosity about the traumatic event and not 'partial' PTSD.
CONCLUSION: These preliminary findings agree with an emerging theme suggesting that, although PTSD can occur after head injury, it is easily over-diagnosed.