Psychotic diseases in the elderly are underdiagnosed due to the limited use of medical resources. Advanced age makes psychoses of any cause less pure and differentiated, since old age adds a cognitive-impairment component to the basal psychotic defect.

We intend to estimate the prevalence of paranoid symptoms in older patients, and to study the many medical conditions associated with psychosis.

We conducted a literature review and we have performed a review of several clinical trials.

We found 12.1% of paranoid symptoms in the elderly with cognitive impairment. In absence of this factor, we found a prevalence of 14.1% for suspicion tendencies, 6.9% for paranoid thoughts and 5.5% for evident delusions. These figures were significantly higher in old black people.

We present a table of the main medical conditions that can produce psychotic symptoms. Some cases of apparently typical delusional disorder can appear as a long-term complication of some of these diseases. If organic factors are subtle and long lasting, the clinical may reproduce a fairly typical delusional disorder and may respond to treatment with neuroleptic drugs.

It seems possible that organic brain factors are more common that we believe, becoming essential a comprehensive study of the old psychotic patient. We should pay more attention to psychotic symptoms in elderly patients and avoid conclusions based on cross-evaluations. Diagnosis will be defined by evolution in most of the cases.