Delusional disorder is traditionally considered a less severe clinical entity than schizophrenia or schizoaffective disorder. From the dimensional approach to psychiatric diagnostic classification it might be necessary redefine the diagnostic classification of psychosis.

To assess differences found in psychopathology, neuropsychology and functioning among schizophrenia, schizoaffective disorder and delusional disorder.

59 patients were included in this study. 30 out of them presented a diagnostic of schizophrenia, 15 patients delusional disorder and 14 schizoaffective disorder. All of them were assessed through different scales including PANSS, GAF, SIX, SCIP and DKEFS Stroop. To compare the different groups ANOVA, Post hoc Bonferroni analysis and X2 test were carried out.

We found statistically significant differences regarding negative symptoms between patients with schizophrenia and delusional disorder, being those less intense and severe in the last ones. In that way, a inversely proportional trend regarding negative and positive PANNS subtypes between schizophrenia and delusional disorder was observed.

In spite of the fact that the delusional disorder is considered less severe disease than other psychosis we only found a less degree of severity for negative symptoms. Further studies with greater sample size must be conducted.