5 May 2004

Cannabis not implicated in stroke in adolescents.

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

Dear Colleagues,

This item provides no evidence that cannabis causes stroke. The authorsclaim it is a possibility but their evidence persuades to the contrary viewon my reading. They even quote the various known 'neuroprotective' andpositive therapeutic effects of cannabis.

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

In order to test a hypothesis that cannabis leads to stroke, it would beappropriate to look at the many 'natural experiments' where cannabis use hasgained popularity (eg. Jamaica, Greece, Australia). I am not aware of anysuch associations being shown. These authors can only find eight otherliterature references to stroke in young cannabis users and they state thatmost are isolated case reports with some being 'more convincing thanothers'. In addition, it would appear that two of them are by these sameauthors reporting one of these exact same cases.

These authors have been conservative and comprehensive in their descriptionsbut have jumped to a conclusion that cannabis use can cause hypotension and'possibly vasospasm .. resulting in cerebellar ischemia'. This is despitetheir stating that 'The neuropharmacologic literature regarding THCgenerally describes neuroprotective effects . as well as therapeutic effectsincluding analgesia, ocular hypotension and antiemesis. In a rat model offocal cerebral ischemia, synthetic cannabinoid agonists have been reportedto reduce infarct volume'. So it is even conceivable that cannabis mightbenefit stroke victims in certain circumstances.

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

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

A report in the Courier Mail (p3, 5/5) stated that "all had apparently beenbinge smoking" which was incorrect (two had possibly been 'binge smoking'while no history was available for the third who may have used no cannabisat all). It also stated that 'the drug has been found to trigger "brainattacks" in teenagers'. This is also inconsistent with my reading of thearticle 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 MalesAssociated With Acute Marijuana Use. Pediatrics (2004) 113;4:365-370