5 May 2004

Cannabis not implicated in stroke in adolescents.

Cerebellar Infarction in Adolescent Males Associated With Acute Marijuana Use. Geller T, Loftis L, Brink DS. Pediatrics (2004) 113;4:365-370

Dear Colleagues,

This item provides no evidence that cannabis causes stroke. The authors claim it is a possibility but their evidence persuades to the contrary view on my reading. They even quote the various known ‘neuroprotective’ and positive therapeutic effects of cannabis.

In one of the three adolescent stroke cases the authors ‘could not get an adequate history of pattern of use’ and this patient had negative THC findings 3 days after supposedly substantial use of the drug. This is inconsistent with my experience as THC remains detectable for many days and sometimes weeks after use. Yet we are quoted a source citing it as a possibility to have a negative qualitative THC finding 3 days after exposure (? a small quantity consumed or ? false negative result). They state that the annual rate of stroke in children is approximately 60 per million (regardless of cannabis use). Clearly in late teens there will be a proportion (in fact, an increasing proportion) who happen to be using cannabis.

In order to test a hypothesis that cannabis leads to stroke, it would be appropriate to look at the many ‘natural experiments’ where cannabis use has gained popularity (eg. Jamaica, Greece, Australia). I am not aware of any such associations being shown. These authors can only find eight other literature references to stroke in young cannabis users and they state that most are isolated case reports with some being ‘more convincing than others’. In addition, it would appear that two of them are by these same authors reporting one of these exact same cases.

These authors have been conservative and comprehensive in their descriptions but have jumped to a conclusion that cannabis use can cause hypotension and ‘possibly vasospasm .. resulting in cerebellar ischemia’. This is despite their stating that ‘The neuropharmacologic literature regarding THC generally describes neuroprotective effects … as well as therapeutic effects including analgesia, ocular hypotension and antiemesis. In a rat model of focal cerebral ischemia, synthetic cannabinoid agonists have been reported to reduce infarct volume’. So it is even conceivable that cannabis might benefit stroke victims in certain circumstances.

Thus there is no strong theoretical reason to suppose that cannabis would cause stroke and these cases do not argue for it in any scientific way either. Casual or coincident use of cannabis in teenagers with other rare illnesses can hardly be taken as evidence of causation.

As ever, this item will be used by those opposing rational drug laws to demand that prohibition is needed more than ever. Yet this very report comes from the United States (St Louis, Missouri) where cannabis use and possession are still severely prosecuted, with very little benefit, it seems, to those intended to be protected such as the tragic cases of the young men described in this report. A recent report showed little difference in cannabis use between San Francisco and Amsterdam where policies are almost opposite.

A report in the Courier Mail (p3, 5/5) stated that “all had apparently been binge smoking” which was incorrect (two had possibly been ‘binge smoking’ while no history was available for the third who may have used no cannabis at all). It also stated that ‘the drug has been found to trigger “brain attacks” in teenagers’. This is also inconsistent with my reading of the article and shows that the journalist did not read it very carefully.

comments by Andrew Byrne ..

Geller T, Loftis L, Brink DS. Cerebellar Infarction in Adolescent Males Associated With Acute Marijuana Use. Pediatrics (2004) 113;4:365-370