Individual differences account for variability when predicting the impact of the traumatic event (Goengian et. al. , 1999; Magwaza, 1999). For example, a diagnosis of PSTD may be confounded by the mergence of a medical disorder (Carver & Harris, 2000). The onset of a life-threatining illness may also lead to clinical symptomatology reflective of PTSD (Brewin, Andrews, & Valentine, 2000; Carver & Harris, 2000). The activity of the physical illness may subside before the symptoms of PTSD diminish (Stuber et al. , 1997).
The diagnosis of PTSD may also be confounded by the existence of cooccuring psychiatric disorders (Mueser et. al. , 1998). Also part of the difficulty in accounting for PTSD is the tendency to under diagnose it, due in part to symptoms common in other disorders (Goodman,k Rosenberg, Mueser, & Drake, 1997). Underreporting of PTSD is common in women with severe and persistent mental illness (Goodman,k Rosenberg, Mueser, & Drake, 1997). Goodman and colleagues (1997) suggested several other reasons for underreporting.
For instance, recollection of events may be confounded by delusional thinking, hallucinations, intoxication, language barriers between the historian and the data collector, amnesia cognitive deficits, and memory impairments (Goodman,k Rosenberg, Mueser, & Drake, 1997). Further, individuals with PTSD may present symptoms that include dissociation, hallucinations, delusional and paranoid thinking, and bizarre behaviors, not unlike the spectrum of psychotic symptoms (Goodman,k Rosenberg, Mueser, & Drake, 1997).
Thus, the level of uncertainty due to common symptom presentation in psychiatric disorders may reduce the likelihood of a PTSD diagnosis. Persons with severe and persistent mental illness (SPMI) are likely to have also experienced a traumatic event (Resnick, 1998). Mueser and her colleagues (1998) discovered that the existence of a least one traumatic event had occurred in 98% of persons with severe mental illness, yet PSTD was diagnosed in only 2% of them.
Whether the person was exhibiting psychiatric disorders of a separate etiology, or the psychiatric disorders were related to a traumatic event in the person’s life, the rate of comorbidity and PTSD appears to be high in those with severe mental illness (Mueser et. al. , 1998). Psychiatric disorders that most commonly occur after a trauma include anxiety disorders, mood disorders, conversion disorders, postconcussion syndromes, dissociative disorders, and occasionally psychoses (Resnick, 1998).
Person with a trauma history presenting concurrent psychiatric disorders still may be accurately assessed and diagnosed with PTSD (Mueser, Salyers, Rosenberg, Ford, Fox, & Carty, 2001) The presence of comorbidity has little impact on reliability and validity when using standardized assestment measures to measure PTSD and symptom severity (Mueser, Salyers, Rosenberg, Ford, Fox, & Carty, 2001).
Mueser and colleagues (2001) administered the Trauma History Questionnaire (THQ; Green, 1996), the Clinician-Administered PTSD Scale (CAPS; Blake Weathers, Nagy, Kaloupek, Gusman, Charney, & Keane, 1996) to 16 women and 14 men who had a primary Axis I diagnoses of a severe and persistent mental illness, and a secondary diagnoses of PTSD. Innterrater, test-retest, and internal consistency reliabilities were found to be moderate to high in all instruments. Convergent validity was moderate on the initial assessment with the CAPS and PSL and stronger on follow-up interviews.