Veterans with both TBI and cannabis use disorder had over 3 times the risk of cognitive disorders compared to those with neither | Research

The takeaway

In a study of 1.56 million US Veterans, those with both traumatic brain injury and cannabis use disorder had a 3.26 times higher risk of developing cognitive disorders, including early-onset dementia, compared to those with neither condition.

VA clinicians managing Veterans with TBI; neurologists assessing cognitive disorder risk factors in military populations.

3.26x cognitive disorder risk with combined TBI and CUD

What the researchers found

Cognitive disorder incidence was highest in Veterans with both TBI and CUD (1.83 per 10,000 person-months), followed by TBI only (1.03), CUD only (0.68), and controls. The hazard ratio for cognitive disorders was 3.26 for TBI+CUD, 2.32 for TBI only, and 1.79 for CUD only. CUD alone was associated with the highest risk of early-onset cognitive disorder other than Alzheimer's and frontotemporal dementia.

Why it matters

TBI and cannabis use are both common in the Veteran population. This study suggests their combination may create compounding cognitive risk beyond what either condition poses alone, with implications for screening and intervention in VA healthcare.

The numbers in context

1,560,556 Veterans (82.32% male, median age 34.51, 61.35% white). Cognitive disorder HR: CUD+TBI 3.26 (95% CI 2.91-3.65). TBI only 2.32 (95% CI 2.13-2.53). CUD only 1.79 (95% CI 1.60-2.00). CUD alone had highest risk of early-onset cognitive disorder.

How the study worked

Retrospective cohort using VA and DoD administrative data from the LIMBIC-CENC Phenotype study, 2003-2022. 1,560,556 Veterans analyzed. Kaplan-Meier survival analysis and Cox proportional hazards models for cognitive disorder incidence.

What this study cannot tell us

Administrative data cannot determine cannabis dose, frequency, or timing relative to TBI. CUD diagnosis codes likely represent severe use, not all cannabis users. Observational design cannot prove causation. Veteran population may not generalize to civilians.

How to read the evidence

Very large Veteran cohort with nearly 20 years of follow-up data. Observational design limits causal inference.

When this study was published

2024 study

The bigger picture

If cannabis use compounds TBI-related cognitive vulnerability, this has direct implications for cannabis policies in VA settings and for counseling Veterans with brain injury history about cannabis use, whether recreational or medical.

Questions still open

Does cannabis use worsen cognitive outcomes after TBI, or do Veterans with worse cognitive trajectories turn to cannabis? Would medical cannabis for TBI-related pain carry the same cognitive risk?

Common questions

Does cannabis cause dementia after brain injury?

This study shows an association, not causation. Veterans with CUD and TBI had higher cognitive disorder rates, but other factors common to this group (PTSD, substance use, blast exposure) could contribute.

What is early-onset cognitive disorder?

Cognitive impairment or dementia developing before the typical age of onset (usually before age 65). The study found CUD alone was particularly associated with this type of cognitive decline.

Read the original research

Cannabis use disorder contributes to cognitive dysfunction in Veterans with traumatic brain injury.

Frontiers in neurology, 15, 1261249

View on PubMed ↗Publisher’s paper ↗

Citation

Esmaeili, Aryan; Dismuke-Greer, Clara; Pogoda, Terri K; Amuan, Megan E; Garcia, Carla; Del Negro, Ariana; Myers, Maddy; Kennedy, Eamonn; Cifu, David; Pugh, Mary Jo. (2024). Cannabis use disorder contributes to cognitive dysfunction in Veterans with traumatic brain injury.. Frontiers in neurology, 15, 1261249. https://doi.org/10.3389/fneur.2024.1261249