Abstract
BACKGROUND: Depression and Post Traumatic Stress Disorder (PTSD) are highly comorbid disorders following trauma exposure; when comorbid they are associated with more deleterious and long-term impact. However, the nature of this relationship lacks consensus and is understudied in adolescence, despite this being highlighted as a critical period for trauma exposure. Cognitive processes such as appraisals, avoidance and rumination have been implicated in both disorders separately and could be potential shared mechanisms underlying this comorbidity. METHOD: In a cross-sectional design, 280 secondary school pupils (12-15 years), reporting trauma exposure, completed self-report measures of Post Traumatic Stress Symptoms (PTSS), depression and maladaptive cognitive processes (trauma-related and depressogenic appraisals, cognitive avoidance and rumination). RESULTS: PTSS and depression symptoms were highly correlated (r = 0.79) and 60-65% of all probable diagnostic cases of PTSD or depression were comorbid. Strong positive correlations were found for negative trauma appraisals, depressogenic appraisals, cognitive avoidance and rumination, with statistically comparable strengths found for both PTSS and depression symptoms. Comparisons of probable diagnostic groups showed all groups endorsed all maladaptive processes although the comorbid group showed the greatest endorsement (and symptomology). Stepwise hierarchical regression models of the maladaptive processes explained 75-77% of the variance. Trauma-related appraisals were found most prominent in predicting both PTSS and depression symptoms although a commonality analysis suggested the interplay between all cognitive variables explained the vast amount of variance. CONCLUSIONS: Cognitive appraisals, cognitive avoidance and rumination appear to be shared cognitive vulnerabilities in PTSD and depression, which may underlie PTSD-depression comorbidity and provide targets for intervention.