Cannabis and psychotic experiences

Abstract

Hamilton 1 outlined the past three decades of research connecting cannabis use to schizophrenia. We add to this narrative by mentioning the value of examining the relation between cannabis use and subthreshold regions of the psychosis continuum. Psychotic experiences are manifestations of psychosis that resemble frank hallucinations and delusions found in psychotic disorders, but are generally less intense, impairing or persistent 2. In the United States, psychotic experiences are 10 times as prevalent as schizophrenia 3, and these experiences are not merely prodromal signs of psychotic disorder. Some individuals who have them will develop schizophrenia, but most will not 4, 5. Therefore, in recent years, researchers and clinicians have begun to grapple with what to make of these experiences. Studying cannabis use and psychotic experiences is useful, because it can help us make a stronger inference about causal direction. Hamilton points out that cannabis use can possibly be a form of self-medication to cope with prodromal symptoms of psychosis or the side effects of anti-psychotic medications. This is less of an issue when studying psychotic experiences, as they are often fleeting and do not necessarily cause significant distress or disruption in and of themselves; many people prove to be unfazed by psychotic experiences, depending on how the experiences are interpreted 6, and psychotic experiences typically do not warrant anti-psychotic medications. That said, cannabis use as a form self-medication is not entirely out of the question. While most people who report a psychotic experience will not develop schizophrenia, they are still at risk for non-psychotic psychiatric disorders 3, chronic health conditions 7, 8, suicidal behaviors 9 and perceived need for help 10, 11. In other words, psychotic experiences indicate the presence of a broad range of mental and physical health problems, and so it is certainly possible that cannabis can be used to self-medicate the underlying stress associated with these problems. Hamilton rightly points out that studying cannabis and psychosis is complicated because of the several confounding factors that interact over time 12. These confounding factors persist when studying psychotic experiences. For example, illicit drug and alcohol use have been associated with life-time psychotic experiences 3, obfuscating the unique correlation between cannabis and psychotic experiences. Social risk factors such as urbanicity 13, as well as childhood trauma and adversity 14, continue to confound any associations that emerge, and can even have interactive and synergistic relationships with cannabis use, resulting in heightened vulnerability to psychotic experiences. Unraveling the relation between cannabis and its potential role in the etiology of psychosis is imperative now more than ever as the prevalence of marijuana use grows in the United States 15. Studying psychotic experiences can not only help us understand psychosis, but can inform strategies to prevent a wider array of mental and physical health problems. None. Preparation of this publication was supported by grant T32AA014125 from the National Institute on Alcohol Abuse and Alcoholism (NIAAA) of the National Institutes of Health (NIH). The content is solely the responsibility of the authors and does not necessarily represent the official views of NIAAA or NIH.