Delusional themes in Body Dysmorphic Disorder (BDD): Comparisons with psychotic disorders and non-clinical Controls

The prevailing nosological classification of body dysmorphic disorder (BDD) encompasses an optional specifier "with absent insight/delusional beliefs" for patients who hold high conviction of the veracity of their disorder-specific beliefs. Yet limited research has examined the explicit nature of delusional beliefs in BDD. The current study therefore aimed to compare themes of delusional ideation in BDD relative to schizophrenia (SCZ) and healthy controls (HCs). Participants had a primary diagnosis of BDD (n = 44) or SCZ (n = 55), or were HCs (n = 55) with no personal or immediate family history of a diagnosable mental health disorder. Assessment of multidimensional delusional ideation was based on the Peters Delusional Inventory (PDI). Results showed that BDD and SCZ groups endorsed significantly more items, and had significantly elevated preoccupation and conviction than the HC group. Only the SCZ group exhibited significantly elevated distress relative to HC participants. In addition, BDD (akin to SCZ) participants were more likely to endorse somatic (appearance-related), control and thought alienation themes than the HC group. These findings suggest that delusional beliefs in BDD may not be strictly appearance-related, but rather span broader themes. This conveys therapeutic implications in terms of designing and administering targeted treatments aimed at delusional thinking in BDD.