Why Cannabis Won't Protect Your Brain From Alcohol

Alcohol has numerous effects on the brain. Some occur immediately and lead to reduced neuronal activity and impaired brain function. These changes dissipate over a period of hours. In contrast, repeated, long-term, exposure to alcohol leads to cell injury and death mainly due to inflammation. Most of the damage occurs within a particular region of the brain called the hippocampus. The hippocampus is critical for the consolidation of new memories. Damage to the hippocampus partially underlies the memory black-outs experienced by alcoholics.

The hippocampus contains lots of endogenous cannabis receptors. My research has shown that it is possible to rescue the hippocampus, and the memory loss, from the consequences of inflammation by exposing the brain every day to low doses of cannabis. I outlined the results of these studies in my TED Talk. Research from my laboratory, as well as many others, has now clarified the benefits of stimulating cannabinoid receptors for the protection of the brain from the effects of inflammation. Given the substantial evidence now available one would predict that stimulation of cannabinoid receptors should protect the brain from the consequences of chronic alcohol consumption.

A recent study examined this prediction. Mice were made alcohol dependent by daily dosing to achieve a blood alcohol level that in humans would produce symptoms of intoxication, including slurred speech, ataxia, and nausea. The scientists used a variety of drugs to clarify the distinct effects of the two known cannabis receptors on alcohol toxicity. Essentially, they tested drugs that either blocked or stimulated each of the cannabis receptors following the chronic alcohol treatment. Their results indicated that blockade of the type-1 cannabinoid receptor could prevent the neural injury due to the chronic brain inflammation.

This is the opposite of what was expected, i.e., the selective blockade of the type-1 receptor was protective against the negative effects of alcohol. Essentially, they demonstrated that cannabis cannot protect the brain from the toxic consequences of long-term alcohol consumption. The authors discovered that drugs that selectively block the type-1 cannabinoid receptor should be investigated for beneficial effects in alcoholics.

Does such a drug exist? Yes, it is called rimonabant. Rimonabant can selectively block the cannabinoid type-1 receptor. Rimonabant has a fascinating history. It was first introduced as an anti-obesity drug and approved for sale in Europe in 2006. It was very effective; scientists had finally discovered an effective anti-obesity drug! However, in 2008 it was withdrawn from sale because it produced serious psychiatric side effects including the increased incidence of depression and suicide. Obviously, continually blocking cannabinoid type-1 receptors is not a good idea even if it does offer protection from the effects of chronic alcohol consumption.