This secondary analysis of a multicenter RCT (N=193 cis-women, mean age 36.3 years) examined whether pretreatment verbal crystallized IQ (cIQ, measured with MWT-B) predicted PTSD symptom reduction (CAPS-5) and dropout over ~15 months in childhood abuse-related PTSD, comparing CPT vs. DBT-PTSD.
Higher baseline cIQ predicted greater PTSD symptom reduction overall (F=4.75, p=0.031, R²=0.024); post-hoc analysis showed this was driven by the CPT group (β=0.274, p=0.013, Bonferroni-corrected p'=0.026, R²=0.065), with no significant association in the DBT-PTSD group (β=0.057, p=0.624). Overall dropout was 32.1% (CPT 39.0% vs. DBT-PTSD 25.5%), but cIQ did not predict dropout in either group.
- The group×cIQ interaction was non-significant (p=0.171), so differential treatment effects cannot be formally concluded; the CPT-specific finding is post-hoc. - Individuals with intellectual disability were excluded, leaving only 3.6% with cIQ <85, restricting generalizability to lower-IQ patients. - Educational level was not controlled for, so the independent contribution of intelligence cannot be separated from educational effects.
Clinicians using CPT for childhood abuse-related PTSD should be aware that patients with lower verbal intelligence may benefit less — consider adapted materials (e.g., simplified worksheets) to broaden access. DBT-PTSD, with its modular and skills-based design, may be a more IQ-neutral option, though this requires replication.
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