Cannabis use limits head impact injury

This study set out to determine if chronic cannabis use would act as a protectant or an exacerbating agent for acute subconcussive head impacts. They used heading a soccer ball as the primary concussive force. It was published in the journal iScience in June 2023.

43 adult soccer players were included in the study. 24 were regular cannabis users (defined as at least once a week for 6 months). Of the cannabis users, 23 primarily used vaping/smoking and 1 used only edibles.

They found that 20 headings of a soccer ball, via a controlled heading model, "significantly impaired the ocular-motor function" in the subjects (controls the position and movement of the eyes to focus on an object-of-interest).

Serum levels of S100B and neurofilament light (NfL) were the primary outcome measures used to determine the effects of 20 controlled soccer headings to judge astrocyte (majority of cells in the human central nervous system) activation and axonal injury (injury to the slender projection of a nerve cell, or neuron, in vertebrates). These measures were chosen because they have a high sensitivity in detecting subconcussive injury.

The authors found "the degrees of impairments were less in the cannabis group compared to controls." 

The following chart created by the authors demonstrates the results of a chemical marker of impairement, NPC:

The authors' concluded:

Our data suggest that chronic cannabis use may be associated with an enhancement of oculomotor functional resiliency and suppression of the neuroinflammatory response following 20 soccer headings.

NPC and S100B reflect different aspects of brain health, but their time-course data suggest a hypothesis that cannabis use may bolster anti-inflammatory properties in the brain to counteract secondary injury, which can lead to expedited recovery and milder functional deficits.

The full text article is here at ScienceDirect.com.