Late psychoses are a heterogeneous group of disorders whose nosology has been controversial throughout history. The concept of dementia praecox introduced by Kraepelin, and based on the progressive deterioration and early onset, has been so dominant in the last decades that few issues have created as much controversy as that schizophrenia can begin in late age. Our purpose is to identify the different obstacles in the research in late psychoses to be able to overcome these limitations and improve the study in this area.

A literature review was achieved using the National Library of Medicine and PubMed search system.

We found historical limitations, because over the last century, different schools of psychiatry have used different nomenclatures and age limits to define late-onset psychotic disorders. Prevailing beliefs in the low frequency of these diseases or in the association of the onset of psychotic symptoms in the elderly with cognitive impairment have interfered with epidemiological research in this area. Moreover, older psychotic patients are often excluded from epidemiological and pharmacological research. Lack of insight and social isolation determine sampling bias and reliability problems.

Seemengly strong knowledge on late-onset schizophrenia is based, in fact, in samples from patients with late paraphrenia or mixed samples. It becomes mandatory to define concepts and establish diagnostic criteria, and to conduct multicenter studies to increase the size of our samples.