A new study has revealed that medical marijuana includes qualities that could protect the brain from long-term damage after a traumatic injury. The protective effects come from the cannabinoid THC (or tetrahydrocannabinol), the major psychoactive component in the cannabis plant. This latest study implies that medical marijuana might one day help reduce the risk of brain damage after critical surgery.
The study examined the effects of THC on injury to the brain from a range of traumatic conditions including hypoxia (lack of oxygen), seizures, and toxic drugs. Each of these conditions can lead to long-term and serious cognitive damage.
Professor Yosef Sarne of Tel Aviv University’s Adelson Center for the Biology of Addictive Diseases, based at the Sackler Faculty of Medicine, led the study. It was published in the journal Behavioural Brain Research and Experimental Brain Research.
Although the beneficial effects of medical marijuana on the brain have been studied previously on animals, these experiments involved trials where relatively high doses of THCs were administered over short periods of time (around 30 minutes); for instance, in a study conducted at the Department of Pharmacology and Toxicology at Virginia Commonwealth University in 2008.
Unlike these previous experiments, Professor Sarne’s new study consisted of animal trials where far lower doses of THCs were used over a longer time period (in comparison with marijuana that is smoked, the trials used doses between 1,000 and 10,000 mg lower than in other studies). According to Sarne’s conclusions, the longer time period for the treatment and the lower dosage not only benefit the brain in reducing the impact of the injury, but this process also prevents possible injury from occurring in the future if THCs are administered before the trauma occurs.
In other words, adopting both pre- and post-conditioning helps to protect the brain. Specifically, Sarne found that if THCs are administered before a brain injury occurs, this could help to build resistance and trigger brain cells to initiate protective measures. If proven in humans, this conclusion would be of great benefit in the cases of surgery that carry a major risk of brain disease, such as open heart surgery or lung operations.
Looking at the other end of the study, the reason for Sarne carrying on with the post-treatment for a long time after a brain trauma occurred is that the risk to the brain is not always seen at the time of the initial condition; it can come from so-termed secondary effects of brain injuries, such as swelling of tissues or the release of toxic chemicals.
To show the pre- and post–medical marijuana benefits on the brain, Sarne undertook a series of trials on mice. For the study, the mice were divided into two groups. In one group, THC was administered before and after a brain injury was induced; in the other group, the brain injury was induced but no THC was administered. When the mice were examined between three and seven weeks after initial injury, the mouse group that had received the THC treatment performed better in behavioural tests than the other group. The tests were designed to measure learning and memory.
Discussing his study’s conclusion, Sarne explains, “Our results suggest that a pre- or post-conditioning treatment with extremely low doses of THC, several days before or after brain injury, may provide safe and effective long-term neuroprotection.”
The effects were not only psychological. Later biochemical studies showed heightened amounts of neuroprotective chemicals in the treatment group compared to the control group. Sarne explains this as THC acting in a way which “modifies brain plasticity and induces long-term behavioral and developmental effects in the brain.”
Sarne’s research suggests that the low-dose/long-time administration triggers certain biochemical processes within the body that help to protect brain cells and stop them from dying. The THC also helps to preserve cognitive function.
In terms of what is actually going on in the brain when medical marijuana is applied, related research by Dr. Esther Shohami that has been published in the British Journal of Pharmacology points to THC acting to reduce the levels of glutamate in the brain (glutamate is a toxic molecule often released after a traumatic brain injury).
It is also thought that THC decreases the levels of free radicals and chemicals that induce inflammation after injury. It is possible that THC also increases the blood supply to the brain. A 2010 study carried out by researchers based at the Adelson Center pointed to similar effects.
In a related study published in 2012, Sarne showed that a low dose of THC has also benefitted mice against the potential brain damage that can be caused by medical anesthetics (particularly pentobarbital-induced deep anesthesia), recreational drugs like ecstasy, and exposure to carbon monoxide.
While THC has been shown to reduce the effects of brain trauma in animal models, it is important to point out that the effects seen in mice may not necessarily be replicated in humans. To show any beneficial effect in people will require some extensive clinical trials. The trials are likely to center on people at risk of brain disease, such as those who suffer from epilepsy. With these “at-risk” groups, it is possible that low-dose THCs could one day be administered as a preventative measure to help offset the risk of cognitive damage.
As part of his continuing investigation, Sarne’s next experiment will test the ability of low doses of THC to prevent damage to the heart, looking at a condition called cardiac ischemia, in which the heart muscle receives insufficient blood flow.
Flickr photo courtesy -Tico-