(PS10-16) Examination of the Variation in PTSD Symptom Presentation by Primary Psychiatric Disorder in Veterans with PTSD and Comorbid SMI

Introduction: Posttraumatic stress disorder (PTSD) is common among individuals with severe mental illness (SMI), inclusive of the diagnostic categories of schizophrenia spectrum, bipolar, and severe and persistent depressive disorders. Individuals with PTSD and comorbid SMI generally experience worse clinical and functional outcomes than those with either type of disorder alone (Fan et al., 2008; Thatcher et al., 2007), but PTSD often remains overlooked when comorbid with SMI. Thus, there is little information regarding how PTSD symptoms might vary in presentation among individuals with different primary SMI diagnoses. Given the substantial heterogeneity across disorders that constitute SMIs (Zumstein & Reise, 2020), investigation of how the core PTSD symptoms might vary by SMI diagnosis is essential to informing clinical assessment and the application of evidence-based treatments for PTSD in this population.

Method: Baseline data from treatment-seeking Veterans (N = 123) with PTSD and comorbid SMI recruited as part of a parent randomized controlled trial were analyzed to better understand pretreatment PTSD symptom presentations by SMI diagnosis. Participants completed baseline assessments for PTSD symptoms (CAPS-IV) and SMI diagnoses (MINI). A one-way multivariate analysis of variance (MANOVA) was conducted using IBM SPSS Statistics 29.0. Primary SMI diagnosis was entered as the independent variable, and the severity scores of symptom Cluster B (re-experiencing), Cluster C (avoidance), and Cluster D (hyper-arousal) were entered as dependent variables. Post-hoc tests were performed to evaluate multiple comparisons between PTSD symptom cluster means by diagnosis.

Result: No main effect was observed across all PTSD symptom clusters by SMI diagnosis (F (6, 236) = 1.33, p = .245; Wilks’ Lambda = .936, η^2 = .033). However, a significant, between-subjects main effect for avoidance symptoms was observed (F (2, 120) = 3.45, p = .035, η_p^2 = .054). Post-hoc tests suggest that avoidance symptoms were significantly lower for individuals diagnosed with a schizophrenia spectrum disorder compared to those diagnosed with bipolar disorder (MD = -8.48, p = .030, 95% CI [-.61, -16.36]). There were no additional between-subjects effects for the reexperiencing or hyperarousal symptom clusters.

Discussion: Results from the current study indicate that PTSD symptom clusters generally present similarly in SMI populations, independent of primary SMI diagnosis, with one exception. Individuals with schizophrenia spectrum disorders reported significantly lower avoidance symptoms than those with bipolar disorder. All individuals in the current study were required to be adherent to a psychotropic medication regimen for inclusion in the parent trial, so these differences may be an artifact of the psychotropics commonly prescribed for schizophrenia versus bipolar disorder. Alternatively, this finding may represent a unique interaction between similar or overlapping features of PTSD (i.e., avoidance) and schizophrenia (i.e., negative symptoms; Lysaker & LaRocco, 2008). Future studies might consider using latent profile analysis (LPA) to acquire a more nuanced understanding of PTSD symptom presentations with comorbid SMI.