Dr. Michael Hart on health: what the evidence says · JRE #1246

What the evidence says 01 / RECORD

The cited figures match a single retrospective study (Nguyen et al., The American Surgeon, 2014) of 446 trauma patients at one Level I trauma center, in which 82 THC-positive TBI patients had 2.4% in-hospital mortality versus 11.5% among THC-negative patients, with THC positivity reported as independently associated with survival after statistical adjustment. Subsequent, larger studies have not consistently replicated this finding: a 2020 retrospective cohort of 854 severe TBI patients across six Ohio trauma centers found that positive THC screening did not predict discharge mortality once age, Glasgow Coma Scale score, injury severity, and other confounders were controlled for, with the authors attributing the earlier result to methodological differences in how the 2014 study handled its statistical model. A 2024 study of 3,729 TBI patients found cannabis-positive patients had a numerically lower mortality rate (3.9% versus 4.8%), but the difference was not statistically significant (p=0.3), and the authors explicitly said they could not replicate the original study's significant survival advantage. A 2020 systematic review concluded that evidence on marijuana exposure and TBI outcomes remains inconclusive, noting only one study had found the mortality connection at all, and calling for larger, better-designed research. The specific 2.4%/11.5% statistic is real but comes from one small, single-center retrospective study whose effect has not been consistently reproduced in later, better-controlled work, and it does not establish a proven protective mechanism of THC on brain injury outcomes.