Previous studies have reported depressive symptoms in patients with persistent delusional disorder (PDD). Patients with PDD and depression may need antidepressants for treatment.

The aim of the study was to compare the sociodemographic profile, clinical presentation and treatment response in patients with PDD with and without comorbid depressive symptoms.

We conducted a retrospective chart review of patients diagnosed with PDD (ICD-10) from 2000 to 2014 (n = 455). We divided the patients into PDD + depression (n = 187) and PDD only (n = 268) for analysis.

Of the 187 patients with PDD + D, only eighteen (3.9%) were diagnosed with syndromal depression. There were no significant differences in sociodemographic profile including sex, marital and socioeconomic status (all P > 0.05). PDD + D group had a significantly younger age at onset ([PDD + D: 30.6 9.2 years vs. PDD: 33.5 11.1 years]; t = 2.9, P < 0.05). There was no significant difference between the clinical presentation including mode of onset, the main theme of their delusion and secondary delusions (all P > 0.3). However, comorbid substance dependence was significantly higher in patients with PDD only. (χ2 = 5.3, P = 0.02). In terms of treatment, response to antipsychotics was also comparable ([> 75% response: PDD + D = 77/142 vs. PDD = 106/179); χ2 = 1.9, P = 0.3). There was a significant difference between the two groups in terms of antidepressant treatment ([PDD + D = 32/187; 17% vs PDD: 17/268; 6%), χ2 = 12.9, P = 0.001).

Patients with PDD + D had significantly earlier onset of illness. These patients may require antidepressants for treatment.

The authors have not supplied their declaration of competing interest.