A systematic review of studies with clinician-rated scales on the pharmacological treatment of delusional disorder

To collect the best available evidence and to compare the first-generation antipsychotics (FGAs) vs. the second-generation antipsychotics (SGAs) in the treatment of delusional disorder (DD). Systematic review including studies evaluating treatment response in DD using clinician-rated scales appearing in PubMed and Web of Science databases from inception till September 2019. Those studies meeting inclusion criteria were selected. Outcomes were summarized into two response categories: (1) response to treatment equal to or greater than 50% and (2) response less than 50%. Biases and quality of the studies were evaluated, and relevant data were extracted. Finally, both narrative review and quantitative synthesis were performed. The final sample included six studies (437 patients, 318 on treatment with SGAs). Antipsychotics achieved a good response in 32.3% of patients. Effectiveness differences between FGA and SGA were only marginal favouring the former. Among the most used antipsychotics, risperidone and olanzapine showed, respectively, 34.3 and 33.7% good response. Pimozide (n = 35) demonstrated a higher response rates compared with other antipsychotics. Inpatients showed the best treatment outcomes. Antipsychotics appeared to be an effective treatment in patients with DD. FGA were slightly superior to SGA. Pimozide does not seem to provide any advantage in most DD subtypes.