Marijuana-Induced Psychosis May Foretell Future Episodes
Psychiatric News February 3, 2006 DOI: 10.1176/pn.41.3.0023 (opens in new tab)
Study at a glance
AI-extracted from the abstract| Characteristics | Observational cohort (register-based follow-up study) Peer reviewed |
|---|---|
| Sample size | 535 |
| Population | Patients treated for a first marijuana-induced psychotic episode in Denmark between 1994 and 1999, identified through the Danish Psychiatric Central Register |
| Duration | Followed for at least three years after the first marijuana-induced psychotic episode |
| Topics | Cannabis |
| Citations | 1 |
| Key findings | Among 535 patients with a first marijuana-induced psychotic episode, 77 percent had subsequent psychotic episodes and 45 percent were later diagnosed with a schizophrenia-spectrum disorder, with most diagnoses made within three years. Those who developed such a disorder did so at a younger age than comparison subjects without a history of marijuana-induced psychotic symptoms, an effect most marked for paranoid schizophrenia. The authors concluded that cannabis-induced psychotic symptoms often mark a first step toward severe psychopathology, though the design could not establish causality. |
Abstract
Back to table of contents Previous article Next article Clinical & Research NewsFull AccessMarijuana-Induced Psychosis May Foretell Future EpisodesJoan Arehart-TreichelJoan Arehart-TreichelSearch for more papers by this authorPublished Online:3 Feb 2006https://doi.org/10.1176/pn.41.3.0023Reports from various researchers have suggested that marijuana-induced psychosis is generally short-lived and that total remission can be expected. Such reports, however, have been based on case studies, not on long-term follow-up data, according to the authors of a new, long-term study.The study found that an episode of marijuana-induced psychosis is not innocuous—it often presages subsequent psychotic episodes and a diagnosis of a schizophrenia-spectrum disorder.Mikkel Arendt, Ph.D., a fellow at the Center for Basic Psychiatric Research at the University of Aarhus in Denmark, and coworkers used the Danish Psychiatric Central Register to identify patients treated for a first marijuana-induced psychotic episode between 1994 and 1999. There were 535 such patients. The researchers then followed those patients for at least three years to determine how many of them experienced subsequent psychotic episodes and how many could be diagnosed with a schizophrenia-spectrum disorder.The researchers found that 77 percent of the subjects incurred subsequent psychotic episodes and that 45 percent could be diagnosed at some time within the next three years or more with a schizophrenia-spectrum disorder. Moreover, of the 45 percent who developed a schizophrenia-spectrum disorder after experiencing marijuana-induced psychosis, 37 percent received such a diagnosis within three years and the remaining eight after three years. Furthermore, those who developed such a disorder did so at an earlier age than did comparison subjects—individuals who developed such a disorder but who had no recorded history of marijuana-induced psychotic symptoms. This effect was most marked for paranoid schizophrenia.“An episode of short-lived psychotic symptoms following cannabis use seems to have great prognostic value.”Thus, “for the majority of patients, cannabis-induced psychotic symptoms proved to be a first step in the development of a schizophrenia-spectrum disorder or other severe psychopathology,” Arendt and his group concluded in their study report, which was published in the December 2005 British Journal of Psychiatry.The results do not prove that marijuana is causally linked with schizophrenia, the researchers stated; owing to the study design, it was not possible to control for potentially confounding factors such as hereditary predisposition, socioeconomic status, or other kinds of drug use. Nonetheless, the researchers concluded, marijuana use might well hasten the onset of schizophrenia since the subjects who developed schizophrenia in the wake of using marijuana did so at a younger age than the comparison subjects.“I think it is important to follow the patients treated for cannabis-induced psychosis closely and to offer them and their relatives information on risk factors for, and early signs of, schizophrenia,” Arendt told Psychiatric News. “Much work is going on around the world trying to find early signs of schizophrenia because the prognosis of patients improves with early intervention. An episode of short-lived psychotic symptoms following cannabis use seems to have great prognostic value.”Eric Strain, M.D., a professor of psychiatry at Johns Hopkins University and chair of APA's Council on Addiction Psychiatry, agreed. “The study suggests that a substance-induced psychotic episode serves as an important indicator identifying a group of patients at high risk for subsequent psychiatric needs.”Nonetheless, Arendt stressed, “Our study does not show that marijuana is a risk factor for young people with a family history of schizophrenia. However, the next phase of our investigation will be a study on hereditary predispositions among those developing schizophrenia following an episode of cannabis-induced psychosis.”An abstract of “Cannabis-Induced Psychosis and Subsequent Schizophrenia-Spectrum Disorders: Follow-Up Study of 535 Incident Cases” is posted at .▪ Br J Psychiatry 2005 187 510 ISSUES New Archived
Comparable studies
Other observational and cohort studies on cannabis, most cited first.
| Study | Year | Design | Participants |
|---|---|---|---|
| High-potency cannabis and the risk of psychosis People with first episode of psychosis and healthy controls from the local population | 2009 | Case-control study | n = 454 |
| Ayahuasca-Assisted Therapy for Addiction: Results from a Preliminary Observational Study in Canada Rural aboriginal population | 2013 | Observational study | |
| Impaired cognitive performance in drug free users of recreational ecstasy (MDMA) Otherwise healthy young people | 2000 | Observational | |
| Continued cannabis use and risk of incidence and persistence of psychotic symptoms: 10 year follow-up cohort study Individuals from the general population in Germany aged 14-24 at baseline | 2011 | Observational cohort | n = 1,923 |
| Cannabis-induced psychosis and subsequent schizophrenia-spectrum disorders: follow-up study of 535 incident cases Patients treated for cannabis-induced psychotic symptoms in Denmark between 1994 and... | 2005 | Observational cohort | n = 535 |