Marijuana may benefit epileptics, scientists say

Marijuana could help to prevent epilepsy in some patients according to a study showing that natural cannabis-like substances in the brain can calm down overactive nerves.

The findings suggest that it may be possible to stimulate the body's own innate cannabinoids - the ingredients of cannabis - to control epileptic seizures, when hyperactive brain cells trigger uncontrollable trembling.

Although the research has been done on animals, scientists believe the discovery could lead to clinical trials in humans to augment the cannabis trials already under way in Britain to study its pain-relieving properties.

Beat Lutz of the Max Planck Institute of Psychiatry in Munich, a member of a pan-European team of researchers led by Giovanni Marsicano, said the study showed that the brain's natural cannabis system was involved in preventing epileptic seizures.

"When the brain's nerve cells begin to fire too much, then there is a huge production of innate cannabinoids which calms everything down," Dr Lutz said.

Anecdotal accounts of cannabis being used to control epileptic fits go back several centuries. Ibn al-Badri, an Arab writer of the 15th century, described how cannabis was used to cure the epileptic son of a caliphate council member. In the 19th century, at least one British doctor working in India used hashish to treat a patient's convulsions, and in the 1970s medical researchers investigated the anti-epileptic properties of cannabis.

The latest research, published in the journal Science, concentrated on the role played by the brain's innate cannabis system - protein "receptors" on the surface of nerve cells that bind with naturally produced cannabinoids. When the scientists produced genetically engineered mice lacking the proteins - called CB1 receptors - they found that the animals suffered excessive epileptic seizures. The researchers were able to identify in which parts of the brain the CB1 receptors work best to prevent fits by calming down overactive nerve cells.

But Dr Lutz warned that giving cannabis to epileptic patients to simulate the body's natural defence against seizures might only work for some people and could harm others depending on the type of seizure.

"We'd rather suggest that a better strategy would be to develop new drugs to target your indigenous cannabinoids," Dr Lutz said. "It is a self-defence system and is only active when it is needed. You don't have it active all the time so flooding the brain all the time with cannabis may not be a good thing."

Leslie Iversen, visiting professor of pharmacology at the University of Oxford and a world authority on cannabis, said the latest research appeared to explain why the brain produced its own cannabis-like substances.

"It's a very beautifully done piece of work and provides another insight into the role of the naturally-occurring cannabis system in the brain," Professor Iversen said. "The research pinpoints the role of natural cannabinoids in damping down the hyperstimulation of the brain."

There are about 60 known chemicals in cannabis, the most active of which is tetrahydrocannabinol (THC). The Medical Research Council has begun cannabis trials with THC to investigate pain relief in people with multiple sclerosis and patients recovering from operations.