The Effect of Changes in Cannabis Exposure on Psychotic Symptoms in Patients With Comorbid Cannabis Use Disorder

abstract

Objective: It remains unclear whether there is an association between severity of cannabis use and psychotic symptom severity over time. Shedding light on this under-researched matter could have clinical implications for this patient group. Methods: This was a secondary analysis of a randomized, parallel-group, superiority, assessor-blinded trial. We followed 60 patients with dually diagnosed psychosis and cannabis use disorders from the Danish CapOpus trial, which included assessments at baseline, post-treatment (6 months) and 10 months. Cannabis use was registered by self-report assisted by timeline follow-back. Psychotic symptoms were measured using the Positive and Negative Syndrome Scale (PANSS) positive, negative, and general symptoms scores. Analyses were adjusted for potential confounders. Results: Patients were classified into four categories: minor use (0–30 joints at baseline and 0–9 joints at follow-up; n = 19), moderate use (0–30 joints at baseline and 10–196 joints at follow-up; n = 11), high (reducing) use (31–240 joints at baseline and 0–9 joints at follow-up; n = 9), and severe use (31–240 joints at baseline and 10–196 joints at follow-up; n = 21). Those with severe and persistent cannabis use (severe use group) had significantly higher scores, as compared to those with minor use, on the positive symptom (17.0, 95% CI [4.7–19.2] vs. 12.7, 95% CI [10.4–15.0], respectively, adjusted p < .009) and general symptom (37.4, 95% CI [34.0–40.8] vs. 29.8, 95% CI [26.3–33.3], respectively, adjusted p < .003) scales at follow-up. The severe use group had significantly higher scores, as compared to the moderate use group, on the negative symptom scale at follow-up (17.4, 95% CI [15.1–19.7] vs. 12.5, 95% CI [9.3–15.6], respectively, adjusted p < .02). On the other hand, patients in the high (reducing) use group demonstrated the greatest improvement in psychotic symptoms on all three measures. Conclusions: These findings are preliminary and more research must be done to elucidate the relationship between cannabis use and psychosis. Treatment of psychosis and comorbid cannabis use disorder could in the future incorporate treatment strategies emphasising encouragement to reduce cannabis use. CapOpus is registered at clinicaltrials.gov (NCT00484302).

KEYWORDS:

• Cannabis
• psychosis
• symptoms
• substance use disorder

Acknowledgments

The authors wish to thank all investigators who were involved in the original conduct of the CapOpus study: Allan Fohlmann, Anne-Mette Larsen, Mette Madsen, Mikkel Arendt, and Christian Gluud.

Disclosures

All authors report no financial relationships with commercial interests with regard to this manuscript.

Funding

The CapOpus trial was funded by the Lundbeck Foundation; the Municipality of Copenhagen; the Egmont Foundation; the Health Insurance Foundation; the Ministry of Social Welfare; Aase and Ejnar Danielsen's Foundation; and the Wørzner Foundation. The funding bodies of the trial had no influence on design, analysis, interpretation, drafting of the manuscript, decision to publish, or any other areas other than funding.

Notes

¹ These groups were defined as 0 to 30 joints at baseline and abstinent at follow-up; 0 to 30 joints at baseline and not abstinent at follow-up; 31 to 240 joints at baseline and abstinent at follow-up; and 31 to 240 joints at baseline and not abstinent at follow-up.