Psychotic depression is defined as a major depressive episode with features of psychosis, such as hallucinations and/or delusions. It mainly occurs in patients with bipolar disorder or major depressive disorder. An estimated 10 to 15 percent of people with severe depression will eventually develop symptoms of psychosis.

Hallucinations may be visual, auditory, olfactory (smell) or tactile (touch). Delusions are usually consistent with the patient’s depressive mood (mood-congruent delusions) but may be inconsistent (mood-incongruent delusions). Examples of mood-congruent delusions might include those of guilt, illness, inferiority or punishment. In contrast, a mood-incongruent delusion might be one of grandeur (such as believing oneself to be a king or a god).

About half of patients with psychotic depression experience more than one kind of delusion, and, in most cases, delusions occur without any hallucinations. Many individuals with psychotic depression also feature severe anhedonia — the inability to experience pleasure — and psychomotor retardation.

Psychotic depression is sometimes confused with or misdiagnosed as schizoaffective disorder, as the two conditions feature similar symptoms. The main difference between the two disorders lies in the primary symptom (depression or psychosis) and the order in which the symptoms present themselves.

In psychotic depression, the primary symptom is depression. Psychotic symptoms typically develop after the patient has had several bouts of severe depression without psychosis. Once psychotic symptoms occur, however, they tend to present themselves with each future depressive episode.

In contrast, the primary symptom in schizoaffective disorder is psychosis. Psychotic symptoms must be present for at least two weeks without any mood symptoms. The prognosis is considered worse for patients with schizoaffective disorder compared to those with psychotic depression.

Onset typically occurs between the ages of 20 and 40 with patients typically experiencing an average of 4 to 9 episodes in a lifetime. Family members of patients with psychotic depression are at greater risk for both psychotic depression and schizophrenia.

Example: The psychiatric patient who had been diagnosed with clinical depression refused to eat his dinner because he believed it had been poisoned. The doctor soon realized that the patient had psychotic depression rather than just major depressive disorder.