Marijuana protects brain in trauma

Frequent use of marijuana has a negative effect on the developing brain. Researchers at Tulane and Dartmouth medical schools looked at the possible protective effect of marijuana in severe head injury. The results were recently published in an article, Preinjury Use of Marijuana and Outcomes in Trauma Patients.

They examined records of adults who presented to two large regional trauma centers between 2014 and 2018. They included patients who had detectable levels of delta-9-tetrahydrocannabinol (THC) in the blood. They excluded those who had other illicit drugs present.

Of the 4849 patients, 1373 (28.3%) had THC present in the blood. These patients tended to be younger, more likely to be males, and more likely to be injured by “penetrating mechanism” than those who did not have THC present. Patients with THC had a shorter hospital stay, shorter need for ventilation, and a shorter stay in the intensive care unit. The mortality rate was somewhat lower in the THC-positive group (4.3% versus 7.6%) but this difference did not reach statistical significance.

The mechanism could be related to the anti-inflammatory effects of marijuana mentioned in the previous post. Head trauma is known to trigger an immune response that leads to inflammation that in turn worsens brain damage. The researchers did not measure any inflammatory markers so this is just a speculation. It is also possible that the THC-positive group did better because it was significantly younger than the THC-negative group.

In another very large chart review study that looked at older trauma patients, intoxication with alcohol predicted better survival and shorter hospital stay. On the other hand, the presence of cocaine or marijuana worsened the prognosis.

In the US, trauma is the leading cause of death and disability in 18 to 44-year-olds. This is also the age group that is more likely to use marijuana. Consuming marijuana may increase the risk of trauma as suggested by the fact that THC-positive patients were more likely to have a “penetrating injury”. Despite the protective effect of marijuana, it is very likely that reducing its use will lead to fewer injuries and more lives saved.