Detection of Psychosis by Rorschach Performance Assessment System Variables in Adolescents With Chronic Daily Cannabis Use
John M. Spores
Ethical Human Psychology and Psychiatry April 1, 2025 DOI: 10.1891/ehpp-2024-0005 (opens in new tab)
Study at a glance
AI-extracted from the abstract| Characteristics | Retrospective case-control study Peer reviewed |
|---|---|
| Sample size | 20 |
| Population | Adolescents without a history of psychosis; 10 daily cannabis users and 10 with no cannabis or other substance use history, matched on sex and age |
| Duration | Daily cannabis use for 6 or more months |
| Measures | Rorschach Performance Assessment System (R-PAS) |
| Topics | Cannabis |
| Key findings | Seven of eight R-PAS perception and thinking variables distinguished daily cannabis-using adolescents from non-using peers, with the cannabis group scoring approximately two to three standard deviations higher and falling in very high or extremely high interpretive categories, which the authors characterize as signs of psychotic disturbance as operationally defined by these R-PAS variables. |
Abstract
A retrospective sample of 20 adolescents without a history of psychosis was divided into two equal groups of 10: one with daily use of cannabis for 6 or more months and one without any history of cannabis or other substance use. The groups were matched on both sex and age. All 20 adolescents were administered the Rorschach Performance Assessment System (R-PAS), which were all determined to be valid protocols. A series of eight independent samplettests with Cohen’sdeffect sizes were done, along with other descriptive and inferential statistics. Results showed that seven of eight perception and thinking R-PAS variables reliably distinguished between the Cannabis and No Cannabis groups. Further, the Cannabis group showed standard scores falling within either the very high or extremely high interpretive categories for this test, hence manifesting unequivocal signs of psychotic disturbance as operationally defined by the perception and thinking R-PAS variables. Further, the Cannabis group scored approximately two to three standard deviation differences on these R-PAS variables versus the No Cannabis group, hence manifesting consistently large effects. Implications of these findings were discussed, including some limitations of the present study and suggestions for future research.
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 |
Citations in the library
Cites 3
- Adolescent Synthetic Cannabinoid Exposure Produces Enduring Changes in Dopamine Neuron Activity in a Rodent Model of Schizophrenia Susceptibility. The International Journal of Neuropsychopharmacology April 1, 2018
- Reversible and regionally selective downregulation of brain cannabinoid CB1 receptors in chronic daily cannabis smokers Molecular Psychiatry July 12, 2011
- Marijuana alters the human cerebellar clock. Neuroreport June 11, 2003