The impact of substance abuse on mortality in patients with severe traumatic brain injury

Background. Drug and alcohol use are common in neurotrauma patients. Despite growing methamphetamine use there are few studies of the impact of methamphetamine use on outcome after traumatic brain injury (TBI). Methods: We conducted a retrospective review of 5-years of data from a trauma database. Inclusion criteria included severe TBI and diagnosis codes indicating head injury. The entire database was analyzed and then a subset of patients with complete toxicology data were examined separately. Primary outcome was mortality. Results. Four hundred eighty-three patients were included. Toxicology re-suits were available for 52.6% of patients. Alcohol, amphetamines, and cannabis were the most commonly detected substances. Overall mortality was 50.9%. When the group with complete tox screen data were analyzed, a toxicology screen that was positive for alcohol or amphetamine was associated with decreased mortality with an odds ratio of 0.23 (CI: 0.10-0.56, p = 0.001) and 0.25 (CI: 0.08-0.79, p = 0.02), respectively. When the subset of patients for whom toxicology data were available was analyzed the amphetamine-positive group was more likely to use cannabis and less likely to use alcohol. Conclusions. We unexpectedly found alcohol and methamphetamine use to be associated with decreased mortality. Neurotoxic and possible neuroprotective mechanisms of these substances are discussed as well as possible interactions between cannabis and methamphetamine. The potential influence of psycho-social factors are also considered. Prospective studies are needed to further investigate the effects of drug and alcohol use on outcome after severe TBI.