Background and Purpose
An increasing number of case reports link cannabis consumption to cerebrovascular events. Yet these case reports have not been scrutinized using criteria for causal inference.
All case reports on cannabis and cerebrovascular events were retrieved. Four causality criteria were addressed: temporality, adequacy of stroke work-up, effects of re-challenge, and concomitant risk factors that could account for the cerebrovascular event.
There were 34 case reports on 64 patients. Most cases (81%) exhibited a temporal relationship between cannabis exposure and the index event. In 70%, the evaluation was sufficiently comprehensive to exclude other sources for stroke. About a quarter (22%) of patients had another stroke after subsequent re-exposure to cannabis. Finally, half of patients (50%) had concomitant stroke risk factors, most commonly tobacco (34%) and alcohol (11%) consumption.
Many case reports support a causal link between cannabis and cerebrovascular events. This accords well with epidemiological and mechanistic research on the cerebrovascular effects of cannabis.
Daniel G. Hackam, MD, PhD, FRCPC
From the Division of Clinical Pharmacology, Department of Medicine, Western University, London, Ontario, Canada.
Correspondence to Daniel G. Hackam, MD, PhD, FRCPC, 1400 Western Rd, London, Ontario, Canada N6G 2V2. E-mail email@example.com