Cannabis and Psychosis: a Critical Overview of the Relationship

Abstract

Interest in the relationship between cannabis use and psychosis has increased dramatically in recent years, in part because of concerns related to the growing availability of cannabis and potential risks to health and human functioning. There now exists a plethora of scientific articles addressing this issue, but few provide a clear verdict about the causal nature of the cannabis-psychosis association. Here, we review recent research reports on cannabis and psychosis, giving particular attention to how each report provides evidence relating to two hypotheses: (1) cannabis as a contributing cause and (2) shared vulnerability. Two primary kinds of data are brought to bear on this issue: studies done with schizophrenic patients and studies of first-episode psychosis. Evidence reviewed here suggests that cannabis does not in itself cause a psychosis disorder. Rather, the evidence leads us to conclude that both early use and heavy use of cannabis are more likely in individuals with a vulnerability to psychosis. The role of early and heavy cannabis use as a prodromal sign merits further examination, along with a variety of other problem behaviors (e.g., early or heavy use of cigarettes or alcohol and poor school performance). Future research studies that focus exclusively on the cannabis-psychosis association will therefore be of little value in our quest to better understand psychosis and how and why it occurs.

Early cannabis use and its relation to the development of psychiatric disorders: a review

“…On the other hand, some authors point out that starting at an early age not only increases the risk of presenting psychosis, but also makes it emerge at younger ages compared to later users or those who never use cannabis (Hall & Degenhardt, 2007;Helle et al, 2016;Konings, Henquet, Maharajh, Hutchinson, & van Os, 2008;Ksir & Hart, 2016;Veen et al, 2004). In a recent meta-analysis, it points out that regular cannabis use precedes the onset of psychosis by 6.3 years (Myles et al, 2016).…”

“…It should also be noted that the age of onset is not the only risk factor, and that, for example, some authors point out that the use of cannabis in high doses is more important (Henquet et al, 2005). Accordingly, cannabis is possibly not a necessary or sufficient cause, but acts amplifying the genetic vulnerability of the individual with other environmental risk factors, in the development of psychotic disorders (Degenhardt, Hall, & Lynskey, 2003;Ksir & Hart, 2016; van Winkel & Genetic Risk and Outcome of Psychosis Investigators, 2011), or advance the appearance of positive psychotic symptoms by up to three years in these individuals (Helle et al, 2016). A systematic review posits the hypothesis that exposure to cannabis, especially during adolescence, could lead to immunological dysfunctions that could potentially cause latent vulnerability for psychosis and, in turn, increase the risk of schizophrenia (Suárez-Pinilla, López-Gil, & Crespo-Facorro, 2014).…”

Psychopathology Related to Energy Drinks: A Psychosis Case Report

“…Current cannabis abuse or dependence increases the risk of transition into psychosis in persons at ultrahigh risk of psychosis [17, 18]. There have been few studies addressing the effects of caffeine and cannabis in combination, but they have been focused on their combined effects on memory but not in psychosis [19].…”

Pathways to care and duration of untreated psychosis in patients with a first episode of psychosis in Italy

“…Many patients used illicit substances, in particular cannabinoids (32.5%). It is likely that at least in some cases the first psychotic symptoms might have been wrongly interpreted by patients and their relatives and misdiagnosed by the first professionals contacted (who in most of the cases were not psychiatrists) as effects of the assumed substances (Ksir & Hart, 2016). Given the rapid increase in the prevalence of substance abuse in Italy (Galimberti et al, 2015), the role of substance abuse deserves adequate attention in the assessment of young patients with mental health problems.…”