Use of THC Concentrates and Risk of Stroke in Adults

Abstract The increasing availability of high-THC cannabis concentrates has raised concerns regarding their potential cerebrovascular effects; however, evidence specific to concentrated THC products remains poorly characterized and is frequently combined with general cannabis exposure. This systematic review aimed to evaluate published evidence describing ischemic or hemorrhagic stroke in adults following identifiable THC-concentrate exposure. The review was conducted in accordance with PRISMA 2020 principles. Eligible studies included adults exposed to identifiable cannabis-derived THC concentrates, including concentrated cannabis resin/hashish and extracted or processed preparations such as THC oils and vaping products, with objectively documented ischemic or hemorrhagic stroke. General cannabis exposure without separable concentrate use, synthetic cannabinoids, and cerebral vasoconstriction without stroke were excluded. Five primary reports met the eligibility criteria, comprising one clinical series and four case-based reports. Reported exposures included cannabis resin/hashish and vaporized THC or cannabis oils. Cerebrovascular presentations included ischemic infarction, subarachnoid hemorrhage, and intraparenchymal hemorrhage. Cerebral vasoconstriction, vasospasm, or reversible multifocal arterial narrowing was a recurring neurovascular finding. However, inconsistent exposure characterization, unverified THC concentrations, possible contaminants, co-exposures, and competing vascular mechanisms substantially limited causal interpretation. Overall, the available evidence remains limited and predominantly case-based. Although recurrent cerebral vasoconstriction represents a clinically relevant signal requiring further investigation, current evidence cannot establish causality or quantify stroke risk attributable specifically to THC concentrates. Prospective studies incorporating standardized assessment of product composition, THC concentration, dose, route, co-exposures, and neurovascular findings are required. Keywords: THC concentrates; cannabis concentrates; stroke; ischemic stroke; intracranial hemorrhage; reversible cerebral vasoconstriction syndrome; cerebral vasospasm; THC vaping.