Association between immediate and early seizures and pre-injury alcohol and marijuana use: A traumatic brain injury model systems national database analysis

This study examined the role that pre-injury alcohol and marijuana use have on the incidence of post-traumatic seizures, as well as their relationship with their known risk factors. We hypothesized that pre-injury alcohol and marijuana use would independently predict post-traumatic seizures at 3 separate time points, categorized as immediate, early, and both immediate and early seizures. 3,875 participants were identified using the Traumatic Brain Injury Model Systems National Database. The primary outcome was the occurrence of a post-traumatic seizure. The primary exposure variables of interest included pre-injury alcohol and marijuana use. Covariates included presence of pre-injury seizures, age and sex at injury, and injury-related characteristics. The relationship between pre-injury alcohol and marijuana use, and each seizure outcome was examined using separate logistic regression models, with results reported as odds ratios with 95% confidence intervals. From the total number of participants 88.8% did not experience seizures, with immediate seizures observed in 269 participants, early seizures observed in 111 participants, and both immediate and early seizures observed in 53 participants. For the immediate seizure group pre-injury alcohol use was not significantly associated with immediate seizures. In the early seizure group, however, alcohol use in the month prior to injury was significantly associated with increased odds, while pre-injury marijuana use was associated with decreased odds. In the combined immediate and early group, alcohol use was not significantly associated, but pre-injury marijuana use was associated with an increased odds of seizure. This study illustrated a possible priming effect of pre-injury alcohol use on post-injury brains, showing a stronger association between the development of early compared to immediate seizures. The effect of marijuana on seizure risk was less clear, nevertheless reinforcing the importance of strong counseling for this vulnerable population, particularly for those with a pre-morbid history of alcohol/substance use.