This cross-sectional SEM study examined how two Reward Probability Index (RPI) subscales — Reward Probability (RPI-RP) and Environmental Suppression (RPI-ES) — relate to four DSM-5 PTSD symptom clusters (Intrusion, Avoidance, negative cognitions/mood [NACM], and hyperarousal [AAR]) in 428 university students, with and without depression as a latent covariate.
RPI-ES showed robust negative associations with all four PTSD symptom clusters across all models (β = −0.44 to −0.68 in joint models). RPI-RP displayed a statistical suppressor effect when modeled alongside RPI-ES, showing counterintuitive positive associations with Intrusion and Avoidance; when modeled alone, RPI-RP showed the expected negative associations with all clusters (β = −0.20 to −0.52). Depression explained additional variance beyond RPI subscales, especially for NACM (ΔR² = 0.12) and AAR (ΔR² = 0.077).
- Sample was predominantly female (~78%) university students earning course credit, limiting generalizability to clinical or more balanced-sex populations. - Cross-sectional design prevents causal inference about reward dysfunction and PTSD. - High intercorrelation between RPI-RP and RPI-ES (r = 0.58) limits interpretability of their independent effects when modeled together.
RPI-ES — which captures perceived availability of rewarding opportunities in the environment — is a strong, depression-independent correlate of PTSD symptom severity across all four clusters; clinicians may consider screening for environmental reward suppression in trauma patients. Incorporating Behavioral Activation components targeting reward availability into standard PTSD treatment may benefit patients with comorbid depression or substance use disorders.
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