Secondary psychoses: an update

Abstract

Psychotic disorders due to a known medical illness or substance use are collectively termed secondary psychoses. In this paper, we first review the historic evolution of the concept of secondary versus primary psychosis and how this distinction supplanted the earlier misleading classification of psychoses into organic and functional. We then outline the clinical features and approach to the diagnosis of secondary psychotic disorders. Features such as atypical presentation, temporal relation to detectable medical cause, evidence of direct physiological causal relationship to the etiological agent, and the absence of evidence of a primary psychotic illness that may better explain the presentation suggest consideration of a secondary psychosis. Finally, we discuss how careful studies of secondary psychotic disorders can help elucidate the pathophysiology of primary, or idiopathic, psychotic disorders such as schizophrenia. We illustrate this issue through a discussion of three secondary psychotic disorders -psychoses associated with temporal lobe epilepsy, velocardiofacial syndrome, and N-methyl Daspartate (NMDA) receptor encephalitis -that can, respectively, provide neuroanatomical, genetic, and neurochemical models of schizophrenia pathogenesis.

A 54-year-old man with hallucinations and hearing loss

“…All of these features are more common in psychosis secondary to general medical condition than in schizophrenia. 1,2 Our patient presented at a relatively late age and had no personal or family history of psychosis.…”

Psychosis in Later Life

“…General features that help to distinguish secondary psychoses from primary disorders include the following: atypical presentation of psychosis (i.e., a later age of onset, the presence of visual hallucinations, or accompanying severe disorientation/confusion), presence of accompanying medical symptoms, temporal relation of psychotic symptoms to a known medical disorder, prescription or over-the-counter medication or substance use, and absence of evidence to support a diagnosis of a primary psychotic illness. 42 Delirium Since delirium can present with psychotic features, particularly in older individuals, it must always be ruled in or out. We should emphasize that a comprehensive review of delirium is beyond the scope of this article, and our discussion here is meant only to provide a brief overview.…”

When apparent schizophrenia is excluded

“…A recent review on secondary psychosis suggests that several questions can be asked to determine whether the psychosis is as a result of a general medical condition (GMC). [14] These include questions on atypicality of presentation as well as temporal and/or physiological relationship to a GMC and/or substances. Additionally, primary illness factors such as age of onset, family history, outcomes and characteristic findings on special investigations should always be considered.…”