Comorbidity between major depressive disorder (MDD) and posttraumatic stress disorder (PTSD) is a well-established fact but has been studied little among MDD patients and even less among outpatients. We assessed the prevalence and characteristics of comorbid MDD-PTSD patients in a sample of MDD outpatients in an effort to elucidate possible causes of MDD-PTSD comorbidity. A semistructured clinical interview was applied to 101 outpatients with MDD. Sociodemographic factors, psychiatric history, the presence of PTSD, and MDD-PTSD comorbidity were recorded. The prevalence of MDD-PTSD comorbidity was 38.6%, with 26.7% suffering currently from PTSD. The average duration of PTSD was 16 years, and in most cases (79.5%) PTSD started earlier than or simultaneously with MDD. Only 28.8% of patients with PTSD had a documented diagnosis in their medical record. The most significant factors predicting MDD-PTSD comorbidity were found to be chronic depression, a history of prolonged or repeated trauma, male gender, a younger age at onset of psychological symptoms, lower education, and a lower level of functioning. Our findings indicate that MDD-PTSD comorbidity still remains an overlooked fact. Prolonged trauma seems to be a major risk factor for MDD-PTSD comorbidity, predisposing subjects to PTSD and later on or simultaneously to comorbidity with MDD.
Keywords: Comorbidity; depression; posttraumatic stress disorder.