Cannabis Use Interacts With Psychosis Vulnerability in Borderline Personality Disorder: La consommation de cannabis interagit avec la vulnérabilité à la psychose dans le trouble de la personnalité limite.

Mirabelli J.; MacKillop J.; Streiner D.; Korostil M. · Canadian journal of psychiatry. Revue canadienne de psychiatrie · 2026

**Background & Methods** This cross-sectional review study analyzed data from 79 outpatients with borderline personality disorder (BPD) to examine whether cannabis use interacts with psychotic-like experiences (PLEs) in relation to BPD symptom severity. Participants completed questionnaires assessing BPD symptom severity, cannabis use patterns, and PLEs, with moderation analyses testing whether cannabis use influenced the association between PLEs and BPD symptoms. **Key Findings** • Cannabis use significantly moderated the relationship between PLEs and BPD symptom severity (ΔR² = 0.069, P = 0.006), with the association between PLEs and BPD symptoms strengthening as cannabis use increased. • A crossover interaction pattern emerged: individuals with low PLEs and high cannabis use demonstrated the lowest BPD symptom scores, while those with high PLEs and high cannabis use exhibited the highest BPD symptom scores. • PLEs also moderated the cannabis-BPD relationship, revealing that cannabis use was negatively associated with BPD symptoms among individuals with low PLEs (β = -0.358, P = 0.018), suggesting heterogeneous treatment responses based on psychosis vulnerability. **Dosage & Administration** Not reported. **Safety & Adverse Effects** Not reported. However, the study identifies cannabis as potentially exacerbating psychotic symptoms in individuals with elevated psychosis vulnerability, and recommends targeted psychoeducation regarding cannabis-related risks for BPD patients with elevated PLEs. **Evidence Quality** This study demonstrates significant methodological limitations. As a cross-sectional design, it cannot establish causality or determine whether cannabis use causes observed symptom changes or vice versa. The small sample size (n=79) from a single outpatient program limits generalizability. The authors explicitly acknowledge that the cross-sectional nature prevents conclusions about whether cannabis is helpful or harmful for any subgroup. The authors recommend longitudinal research to clarify temporal relationships between cannabis use, PLEs, and BPD symptoms. These findings suggest clinically meaningful heterogeneity warranting further investigation but should be interpreted cautiously pending prospective studies.

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