Even if neurocognition is known to affect functional outcomes in schizophrenia, no previous study has explored the impact of cognition on functionality in delusional disorder (DD). We aimed to assess the effect of clinical characteristics, symptom dimensions and neuropsychological performance on psychosocial functioning and self-perceived functional impairment in DD.

Seventy-five patients with a SCID-I confirmed diagnosis of DD underwent neurocognitive testing using a neuropsychological battery examining verbal memory, attention, working memory and executive functions. We assessed psychotic symptoms with the Positive and Negative Syndrome Scale, and calculated factor scores for four clinical dimensions: Paranoid, Cognitive, Affective and Schizoid. We conducted hierarchical linear regression models to identify predictors of psychosocial functioning, as measured with the Global Assessment of Functioning scale, and self-perceived functional impairment, as measured with the Sheehan’s Disability Inventory.

In the final linear regression models, higher scores in the Paranoid (β = 0.471, p < .001, r² = 0.273) and Cognitive (β = 0.325, p < .001, r² = 0.180) symptomatic dimensions and lower scores in verbal memory (β = −0.273, p < .05, r² = 0.075) were significantly associated with poorer psychosocial functioning in patients with DD. Lower scores in verbal memory (β = −0.337, p < .01, r² = 0.158) and executive functions (β = −0.323, p < .01, r² = 0.094) were significantly associated with higher self-perceived disability.

Impaired verbal memory and cognitive symptoms seem to affect functionality in DD, above and beyond the severity of the paranoid idea. This suggests a potential role for cognitive interventions in the management of DD.