A 2025 Wright State University-led study of 246 deceased Ohio drivers reviewing fatal crashes over a six-year period found that nearly 42% tested positive for THC with an average blood concentration of 30.7 ng/mL.
January 01, 2025
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study_result
Toxicology results from autopsies of deceased drivers were analyzed to assess presence and levels of THC.
THC (tetrahydrocannabinol) is the primary psychoactive compound in the cannabis plant and is responsible for the euphoric 'high' associated with marijuana use.
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definition
Basic pharmacological description of cannabis constituents.
U.S. states use varying per se THC blood-concentration limits for driving enforcement; some states set limits around 2 ng/mL, other states set limits around 5 ng/mL, and some states maintain zero-tolerance laws where any detectable THC can be grounds for a DUI or may require proof of impairment.
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legal
Overview of state-level regulatory approaches to THC and driving.
Clinical and toxicology experts report that THC can impair driving by slowing reaction time, reducing coordination, and impairing judgment, and that higher-potency cannabis products or any detectable THC may increase or prolong driving impairment.
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Summarizes expert and emerging-research conclusions about cannabis impairment and driving safety.