The use of marijuana is associated with a marked increase in the risk of being involved in severe trauma particularly motor vehicle collisions. In 2009, for instance, marijuana use was a contributing factor in more than 460,000 emergency department visits in the United States.
But we also know that cannabis is potentially neuroprotective. Previous studies have found that tetrahydrocannabinol (THC), the active ingredient in marijuana, may have beneficial effects in certain types of neurodegenerative processes, like Alzheimer’s and Huntington’s disease. In addition, previous studies indicate THC may protect the brain in animal models of neurologic injury. However, clinical trials of a synthetic THC derivative were not ultimately associated with an increase in survival in patients with traumatic brain injury. Since overall findings were mixed, we hypothesized that use of the “native” form of THC could be associated with an increase in survival in patients with traumatic brain injury.
In attempting to answer this question, we performed a study, which is published in the October edition of The American Surgeon. Our research team at the Los Angeles Biomedical Research Institute retrospectively surveyed the records of patients admitted to a large urban hospital from Jan. 1, 2010, to Dec. 31, 2012. During this period, 446 patients with traumatic brain injuries had undergone a urine test for THC and other drugs. We found 82 (18.4%) of the patients were positive for THC. Overall, 44 (9.9%) patients died. However, patients testing positive for THC had a death rate of only 2.4% compared to a mortality of 11.5% in patients without THC in their systems. Adjusting for differences between the groups (most notably age), THC was still associated with survival after traumatic brain injury.
Clinical studies of traumatic brain injury are difficult. It is rare that the head injury is the only wounding present. While the vast majority of patients in this study had multiple injuries, most of the deaths were related to the neurologic injury. In addition, the overall injury severity score and brain injury scores were similar between the two groups. This general similarity could lead one to the conclusion that the presence of THC is potentially neuroprotective. This study was one of the first in a clinical setting to specifically associate THC use as an independent predictor of survival after traumatic brain injury.
Another interesting finding relates to the association of alcohol consumption with survival after brain injury. In previous studies, the presence of alcohol appeared to have a protective effect. However, in these investigations, the presence of THC was not evaluated, despite the fact that some patients may have screened positive for both. In this study, we did evaluate for the presence of alcohol, and it appears that THC was more closely associated with survival.
The findings should not be terribly surprising. Critical care physicians use psychoactive medications frequently. The neuroprotective effects of these compounds, thought to be at least partially mediated by their anti-inflammatory properties, are well demonstrated. We know that adequate sedation and pain control in traumatic brain injury is associated with decreasing intracranial pressures and survival. It is possible that our findings as they relate to THC are mediated by similar mechanisms. However, more controlled clinical study is needed.
David S. Plurad, MD, is a researcher at the Los Angeles Biomedical Research Institute and a critical care surgeon at Harbor-UCLA Medical Center.