Psychotic Depression - Differential Diagnosis

Differential Diagnosis

PMD is most frequently confused with NPMD, but it may also be mistaken for the schizophrenia spectrum disorders, including schizoaffective disorder. These are differentiated from PMD by the presence of psychotic symptoms outside of a major depressive episode. In a schizoaffective patient, hallucinations and delusions will occur in the absence of major depressive episodes.

Schizophrenia generally has more disordered thinking and delusional symptoms than PMD. It is unusual for PMD patients to show flight of ideas, loose association, echolalia (repeating what others say), word salad (meaningless speech), and other elements of thought disorders that characterize schizophrenia. Likewise, the presence of bizarre delusions ("Aliens have planted a receiver in my head") appears to be less common in PMD than schizophrenia. However, neither bizarre delusions, nor marked thought disorder necessarily eliminate a diagnosis of PMD. Bipolar disorder can sometimes present with PMD. It is estimated that as many as 42% of patients with PMD in adolescence or young adulthood are likely to develop some type of manic episode later. It is important to take a history of manic symptoms in any younger patient who presents with PMD.

Other psychotic disorders with which PMD is sometimes confused include delusional disorder, substance induced psychotic disorder (with MDD), post-psychotic depressive disorder of schizophrenia, and brief psychotic disorder. The primary way of distinguishing between PMD and any of these disorders lies more in evaluating the course of the illness rather than simply identifying specific symptoms.