Objectives: The aims of this study were to investigate the prevalence, as well as the clinical, cognitive, and functional correlates of psychiatric comorbidity in patients with delusional disorder (DD).
Methods: Eighty-six outpatients with DSM-IV DD were evaluated for psychiatric comorbidity on Axis I disorders using the Mini International Neuropsychiatry Interview (MINI). The following instruments were administered: the Standardized Assessment of Personality (SAP), the Positive and Negative Symptom Scale (PANSS), the Montgomery-Asberg Depression Rating Scale (MADRS), a neuropsychological battery (consisting of measures for attention, verbal and working memory, and executive functions), the Sheehan Disability Inventory (SDI), and the Global Assessment of Functioning (GAF) scale. A socio-demographic and clinical questionnaire was also completed.
Results: Forty-six percent of the subjects had at least one additional lifetime psychiatric diagnosis, the most common being depressive disorders (N = 16, 32.6%), followed by anxiety disorders (N = 8, 14%). DD with comorbid Axis I disorders (N = 40, 46.5%) was associated with a specific syndromic constellation (more common cluster C personality psychopathology, somatic delusions, olfactory and gustatory hallucinations, and suicide risk), and greater severity of the psychopathology, particularly as regards emotional dysregulation (total and general PANSS scales, MADRS, and perceived stress SDI scoring). In contrast, DD without psychiatric comorbidity - "pure" DD - (N = 46, 53.5%) was associated with worse overall neurocognitive performance, mainly in working memory. There were no differences in functionality between the two groups (as per the GAF and SDI total, work, social and family life disability scores).
Conclusions: Our findings reveal one type of DD with associated psychiatric comorbidity with greater emotion-related psychopathology and another "pure" DD, without psychiatric comorbidity, related to worse global cognitive functioning. Treatment for DD should address both types of processes.