Alcohol confounds relationship between cannabis misuse and psychosis conversion in a high‐risk sample
Andrea M. Auther, Kristin Cadenhead, Ricardo E Carrión, Jean Addington, Carrie E. Bearden, Tyrone D. Cannon, Thomas H. McGlashan, Diana O. Perkins, Larry J. Seidman, Ming T. Tsuang, Elaine F. Walker, Scott W. Woods, Barbara Cornblatt
Acta Psychiatrica Scandinavica January 9, 2015 DOI: 10.1111/acps.12382 (opens in new tab)
Study at a glance
AI-extracted from the abstract| Characteristics | Observational cohort Longitudinal Peer reviewed |
|---|---|
| Sample size | 370 |
| Population | Clinical high-risk (CHR) participants enrolled in the North American Prodrome Longitudinal Study Phase 1, mean age 18.3 |
| Duration | Followed for at least 2 years |
| Topics | Cannabis |
| Citations | 46 |
| Key findings | Cannabis abuse/dependence predicted psychosis conversion more strongly than no use or non-impairing use, but the association weakened after adjusting for alcohol use, indicating confounding. Non-impairing cannabis use was not related to psychosis. The authors argue that other substance use must be controlled for to avoid overstating the cannabis/psychosis link. |
Abstract
Objective: Cannabis use has been examined as a predictor of psychosis in clinical high-risk (CHR) samples, but little is known about the impact of other substances on this relationship.
Method: Substance use was assessed in a large sample of CHR participants (N = 370, mean age = 18.3) enrolled in the multisite North American Prodrome Longitudinal Study Phase 1 project. Three hundred and forty-one participants with cannabis use data were divided into groups: No Use (NU, N = 211); Cannabis Use without impairment (CU, N = 63); Cannabis Abuse/Dependence (CA/CD, N = 67).
Participants: (N = 283) were followed for ≥2 years to determine psychosis conversion.
Results: Alcohol (45.3%) and cannabis (38.1%) were the most common substances. Cannabis use groups did not differ on baseline attenuated positive symptoms. Seventy-nine of 283 participants with cannabis and follow-up data converted to psychosis. Survival analysis revealed significant differences between conversion rates in the CA/CD group compared with the No Use (P = 0.031) and CU group (P = 0.027). CA/CD also significantly predicted psychosis in a regression analysis, but adjusting for alcohol use weakened this relationship.
Conclusion: The cannabis misuse and psychosis association was confounded by alcohol use. Non-impairing cannabis use was not related to psychosis. Results highlight the need to control for other substance use, so as to not overstate the cannabis/psychosis connection.
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
Cited by 11
- Occasional cannabis use is associated with higher premorbid functioning and IQ in youth at clinical high-risk (CHR) for psychosis: Parallel findings to psychosis cohorts Schizophrenia Research July 30, 2024
- Assessing evidence supporting cannabis harm reduction practices for adolescents at clinical high-risk for psychosis: a review and clinical implementation tool. Psychological Medicine 2024
- Recreational cannabis use over time in individuals at clinical high risk for psychosis: Lack of associations with symptom, neurocognitive, functioning, and treatment patterns. Psychiatry Research August 1, 2023
- Recommendations for Reducing the Risk of Cannabis Use-Related Adverse Psychosis Outcomes: A Public Mental Health-Oriented Evidence Review Journal of dual diagnosis July 3, 2023
- Measurement invariance between online and paper-and-pencil formats of the Launay-Slade Hallucinations scale-extended (LSHS-E) in the Chilean population: Invariance between LSHS-E formats. Current Psychology January 17, 2022
and 6 more in the library
Cites 5
- Continued cannabis use and risk of incidence and persistence of psychotic symptoms: 10 year follow-up cohort study BMJ March 1, 2011
- Effects of cannabis use on outcomes of psychotic disorders: systematic review The British Journal of Psychiatry October 31, 2008
- The Impact of Cannabis Use on Cognitive Functioning in Patients With Schizophrenia: A Meta-analysis of Existing Findings and New Data in a First-Episode Sample Schizophrenia Bulletin July 25, 2010
- Prospective study of cannabis use in adolescents at clinical high risk for psychosis: impact on conversion to psychosis and functional outcome Psychological Medicine December 1, 2012
- Temporal Association of Cannabis Use with Symptoms in Individuals at Clinical High Risk for Psychosis Schizophrenia Research September 21, 2008