Cannabis Use — THC Enters the Bloodstream
Placeholder lead: THC absorbs quickly, blood level spikes within minutes of use.
- ~10 min: Time to peak THC (placeholder, smoked route)
- 10–35%: Bioavailability (placeholder, smoked route)
- Seconds: Onset of effects (placeholder, subjective)
- ~1 hr: Half-life (initial) (placeholder, distribution phase)
Placeholder heading — absorption and distribution
Placeholder body text: THC is lipophilic, absorbs fast, redistributes into fat.
Driving-Relevant Skills Decline at Peak THC
Placeholder lead: reaction time, divided attention, and lane tracking all worsen.
- ~20%: Reaction time slowdown (placeholder, near peak)
- Notable: Lane deviation increase (placeholder, simulator studies)
- Impaired: Divided attention (placeholder, dual-task cost)
- 1–4 hr: Impairment window (placeholder, typical)
Placeholder heading — which skills degrade
Placeholder body text: attention splitting and tracking tasks suffer most.
Blood Level No Longer Predicts Impairment Well
Placeholder lead: unlike BAC, THC level and actual impairment drift apart.
- Weak: THC-impairment correlation (placeholder, post-peak)
- Strong: Alcohol correlation (placeholder, tight BAC link)
- Variable: Tolerance effect (placeholder, frequent users)
- High: Individual variability (placeholder, metabolism)
Placeholder heading — why the link breaks down
Placeholder body text: fat storage and tolerance decouple level from effect.
THC Detectable Long After Impairment Ends
Placeholder lead: metabolites linger in blood and urine for days to weeks.
- ~4–8 hr: Impairment resolves (placeholder, typical)
- Days: Blood detection window (placeholder, frequent users longer)
- Weeks: Urine detection window (placeholder, frequent users)
- Hours: Alcohol detection window (placeholder, matches impairment)
Placeholder heading — the long metabolite tail
Placeholder body text: THC-COOH persists in fat, released slowly over time.
Why This Complicates Impaired-Driving Law
Placeholder lead: a positive THC test does not confirm current impairment.
- Elevated: False-positive risk (placeholder, post-use testing)
- Contested: Legal per-se limits (placeholder, jurisdictions vary)
- Limited: Field sobriety value (placeholder, cannabis-specific)
- Reliable: Alcohol BAC standard (placeholder, established link)
Placeholder heading — policy implications
Placeholder body text: testing reform and behavioral measures are being explored.
Placeholder highlight: detection is not the same as impairment.