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.