The Exaggerated Hazards of Marijuana & Driving NORML Conference   Denver, April 23, 2011 By Dale Gieringer, Ph.D. Director...
Adverse Effects on Driving <ul><li>Studies show MJ  can  impair: </li></ul><ul><li>Concentration </li></ul><ul><li>Complex...
Driving Tests Show Impairment from THC <ul><li>Berghaus meta-analysis of 761 driving study tests: </li></ul><ul><li>> 50% ...
Urine Tests Don’t Measure Impairment! From GM  Ellis  et al.,  Excretion patterns of cannabinoid metabolites after last us...
Cannabis Doesn’t Show in Urine For Several Hours Standard Cutoff = 50 ng/ml
High Blood THC Shows Recent Use <ul><li>Sharp THC peak in first <1 hour after smoking </li></ul><ul><li>THC detectable >12...
Odds Ratios  of Accident Culpability for THC and Alcohol Culpability Odds Ratios  Location  #N  Study    Alcohol (>.08-.1%...
Interpreting Drug Tests <ul><li>•  Urine metabolites not correlated to risk </li></ul><ul><li>•  THC  ≤  2-3 ng =  no incr...
Crancer Study: “Passage of California Cannabis Initiative Will Increase Traffic Deaths :  Marijuana May Overtake Alcohol a...
CA Auto Fatality Rates  1999-2008
Fatal Accident Rates by State - 2008 State  Rank  Fatalities/100m mi. Source: FARS http://www-fars.nhtsa.dot.gov/States/St...
U.S. Auto Fatality Rate Declined  While Marijuana Use Soared in ‘60s & ‘70s Marijuana Use Soars (Prop. 215) (Prohibition R...
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The Exaggerated Hazards of Marijuana & Driving

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The Exaggerated Hazards of Marijuana & Driving

  1. 1. The Exaggerated Hazards of Marijuana & Driving NORML Conference Denver, April 23, 2011 By Dale Gieringer, Ph.D. Director, California NORML “ Legalizing marijuana would mean slaughter on the highways” - Harry Anslinger, Federal Bureau of Narcotics Commissioner
  2. 2. Adverse Effects on Driving <ul><li>Studies show MJ can impair: </li></ul><ul><li>Concentration </li></ul><ul><li>Complex reaction time </li></ul><ul><li>Peripheral vision </li></ul><ul><li>Steadiness of speed, distance </li></ul><ul><li>Decision making skills </li></ul>
  3. 3. Driving Tests Show Impairment from THC <ul><li>Berghaus meta-analysis of 761 driving study tests: </li></ul><ul><li>> 50% showed impairment from THC </li></ul><ul><li>3 showed improvement </li></ul><ul><li>Effects strongest for 2.5 hrs </li></ul><ul><li>Weaker effects to 4 hrs </li></ul>70% impaired after 20-40 min.
  4. 4. Urine Tests Don’t Measure Impairment! From GM Ellis et al., Excretion patterns of cannabinoid metabolites after last use in a group of chronic users. Clin Pharmacol Ther 1985;38(5):572-578.)
  5. 5. Cannabis Doesn’t Show in Urine For Several Hours Standard Cutoff = 50 ng/ml
  6. 6. High Blood THC Shows Recent Use <ul><li>Sharp THC peak in first <1 hour after smoking </li></ul><ul><li>THC detectable >12 hrs at 1-3 ng </li></ul><ul><li>(6+ days in regular users) </li></ul><ul><li>Oral THC slowly reaches low plateau of 5-10 ng/ml </li></ul><ul><li>Blood THC does not track subjective effects! </li></ul>Peak in THC Oral Dose
  7. 7. Odds Ratios of Accident Culpability for THC and Alcohol Culpability Odds Ratios Location #N Study Alcohol (>.08-.1%) THC ( only ) 1= Low Risk; 2-3 Moderate; >5 High Risk New York 497 Terhune & Fell (1982) 5.7 2.1 California 440 Williams et al (1985) 5.0 0.2 U.S. 1,882 Terhune et al (1992) 5.7 0.7 Australia 1,045 Drummer (1994) 5.5 0.7 Australia 2,500 Hunter & Longo (1998/2000) 6.8 0.36 (<1 ng) 1.8 (>2ng) Colorado 414 Lowenstein ((2001) 3.2 1.1 (urine) Maryland 5,573 Soderstrom (2005) 7.45 1.2 (urine) Australia 3,398 Drummer et al (2004) 6.0 2.7 (>1 ng 6.6 (>5 ng) France 10,748 Laumon (2005) 3.0 - 6.2 (BAC≥.10) 2.01 (BAC≤.05) 1.78 U.S. 32,543 Bédard (2007) 8.51 3.3 (BAC≤05) 1.29
  8. 8. Interpreting Drug Tests <ul><li>• Urine metabolites not correlated to risk </li></ul><ul><li>• THC ≤ 2-3 ng = no increased risk </li></ul><ul><li>THC in blood = Alcohol at .05% (moderate) </li></ul><ul><li>THC ≥ 5 ng ~ DUI </li></ul><ul><ul><li>With exceptions! (ADD patient w/ 71 ng in blood) </li></ul></ul><ul><li>THC + alcohol = high DUI risk </li></ul><ul><li>=> More marijuana use could raise or lower overall accident risk depending on whether it substitutes for alcohol. </li></ul>
  9. 9. Crancer Study: “Passage of California Cannabis Initiative Will Increase Traffic Deaths : Marijuana May Overtake Alcohol as a Major Contributing Factor in Fatal Crashes “ Source:Alfred & Alan Crancer: The Involvement of Marijuanain California Fatal Motor Vehicle Crashes 1998-2004 Marijuana involvement in fatal accidents up from <2% to >5% in CA Jump in 2004
  10. 10. CA Auto Fatality Rates 1999-2008
  11. 11. Fatal Accident Rates by State - 2008 State Rank Fatalities/100m mi. Source: FARS http://www-fars.nhtsa.dot.gov/States/StatesFatalitiesFatalityRates.aspx State Rank Fatalities/100m mi. Green = Medical MJ States Blue = Decrim, Non-MMJ States
  12. 12. U.S. Auto Fatality Rate Declined While Marijuana Use Soared in ‘60s & ‘70s Marijuana Use Soars (Prop. 215) (Prohibition Repealed) => Fears of slaughter on the highway due to marijuana are unwarranted!

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