Psychosis Among Substance Users

Jagadisha Thirthalli; Vivek Benegal

Disclosures

Curr Opin Psychiatry. 2006;19(3):239-245. 

In This Article

Abstract and Introduction

Purpose of Review: This work reviews the evidence that substances of abuse can cause psychosis in nonpsychotic persons. The review is based on the concept that psychosis exists in continuum. Studies examining substance use in, or its effect on, already psychotic individuals were not reviewed.
Recent Findings: A substantial proportion of substance users experience psychosis. Use of cocaine, amphetamines, cannabis and alcohol seems to be associated with greater risk for psychosis. Severity and duration of use, age at the time of first use and vulnerability to develop psychosis by virtue of familial, possibly genetic and personality factors seem to be the determinants for the development of psychosis. Epidemiological and preliminary biological studies suggest that cannabis is a component cause in the development of schizophrenia. Evidence for the causative role of other substances is less systematic.
Summary: There exists strong evidence that abuse of substances is associated with greater risk for psychosis and preliminary evidence for their causative role in the development of psychosis. More systematic examination of this issue is likely to throw light on the neurobiology of psychosis and possibly help the vulnerable population in primary prevention.

Psychosis and substance abuse co-occur more frequently than can be explained by chance alone.[1,2] This may be because substance abusers are at a higher risk of developing psychosis and also because psychotic patients are at a high risk of developing the tendency for substance abuse. This review focuses on the former issue: psychosis among users of alcohol and illicit substances, namely, cannabis, amphetamines, cocaine, opioids, phencyclidine (PCP), hallucinogens and inhalants. Such differentiation of co-occurring problems is, no doubt, artificial as common vulnerabilities are likely to underlie the development of both disorders.

Knowledge about psychotic experience among substance abusers is important in several ways. Abused substances act on specific neurotransmitter systems. Studying the mechanism by which they impact these systems to produce psychosis could provide important clues about the pathophysiology of psychotic disorders. Information on the psychotogenic properties of specific substances may be useful in evaluating the risk of developing psychosis among drug users. Violence, aggression and crime are known to be more frequent among persons who have both psychotic symptoms and tendency for substance use than either alone.[3,4] Knowledge about the frequency of psychosis among users of different substances and their specific vulnerabilities may be useful from a forensic psychiatric perspective.

Although much research is taking place on psychosis in relation to certain substances like cannabis and amphetamines, there has been little recent research regarding other drugs. For each substance reviewed here, we begin with the review of important research and expert opinion, regardless of the year of publication; we follow that with an examination of the literature from the past few years. The concept that psychosis exists in a continuum rather than as an all-or-none phenomenon has gained popularity in the recent past.[5] In consonance with this approach, four different lines of research can be identified. They include the study of (a) psychotic experiences among healthy volunteers upon experimental exposure to substances, (b) transient psychotic experiences among epidemiological or clinical populations of substance abusers, (c) short-lasting syndromes of substance-induced psychoses and (d) the causative role of these substances in schizophrenia and related psychoses.

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