JAMA Netw Open

Does traumatic brain injury raise ALS risk?

October 7, 2025

Traumatic brain injury (TBI) is associated with an increased risk of ALS, concentrated in the first 2 years after injury. This pattern raises the possibility of reverse causality, where early ALS symptoms may predispose to TBI, rather than TBI causing ALS.

Study details: This U.K.-wide, population-based cohort study analyzed electronic health records of 85,690 individuals with TBI and 257,070 matched general-population comparators. The aim of the study was to determine whether TBI increases the risk of developing ALS, and whether this risk varies over time following injury.

Results: During follow-up, 150 incident ALS cases were identified. ALS incidence was significantly higher in the TBI group (hazard ratio [HR], 2.61; 95% confidence interval [CI], 1.88-3.63; P<0.001), with 0.08% of TBI patients vs. 0.03% of comparators developing ALS. Notably, the risk was highest in the first 2 years post-TBI (HR, 6.18; 95% CI, 3.47-11.00) and attenuated thereafter, with no difference in ALS risk beyond 2 years. Age at ALS diagnosis and death didn't differ between groups.

Source:

Zhu X, et al. (2025, October 1). JAMA Netw Open. Traumatic Brain Injury and Risk of Amyotrophic Lateral Sclerosis. JAMA Netw Open. https://pubmed.ncbi.nlm.nih.gov/41037265/