Cannabis and Stroke

Abstract

It is likely that there is an association between cannabis and ischemic stroke and transient ischemic attack (TIA). There are multiple reports of mainly younger men, with no vascular risk factors other than tobacco and alcohol use, with symptom onset during or soon after cannabis use. This often follows a marked increase in cannabis intake. The strokes are mainly in the posterior circulation possibly reflecting a greater susceptibility to cannabis induced autonomic changes. Population based studies and retrospective audits have also found an association between ischemic stroke and TIA and cannabis. The numbers of patients using cannabis and presenting with stroke has been increasing in recent years and moves toward legalization for medical and recreational reasons will further increase these numbers. However, a causal association between cannabis and ischemic stroke has not been proven. One of the major confounding factors is tobacco, which is often smoked with cannabis. A causal link between cannabis and stroke is plausible, and a number of lines of evidence point to such a link. These include the temporal association between cannabis use and stroke, and recurrent stroke with cannabis reexposure. Cannabis is associated with myocardial infarction and atrial fibrillation. Myocardial infarction and atrial fibrillation both increase the risk of cardiac embolism, which in turn accounts for 20–25% of ischemic strokes. There is also a reversible cerebral cannabis arteriopathy with reversible vasoconstriction syndrome (RCVS), and (possibly) a more prolonged stenosis of cerebral arteries that has been called multifocal arterial stenosis (MIS). In this chapter, the evidence linking stroke and cannabis, and the lines of evidence pointing to a causal link, will be summarized.