[DT]
Gearhead Surf Coder
mushroomedmario said:most of my friends are better drivers when they're high
Wrong. They *think* they're better drivers.
Scientific data: THC impairs a person's ability to drive.
Quote:
Drug Alcohol Depend. 2004 Feb 7;73(2):109-19.
Dose related risk of motor vehicle crashes after cannabis use.
Ramaekers JG, Berghaus G, van Laar M, Drummer OH.
Experimental Psychopharmacology Unit, Department of Neurocognition, Faculty of Psychology, Maastricht University, P.O. Box 616, MD 6200 Maastricht, The Netherlands. j.ramaekers@psychology.unimaas.nl
The role of Delta(9)-tetrahydrocannabinol (THC) in driver impairment and motor vehicle crashes has traditionally been established in experimental and epidemiological studies. Experimental studies have repeatedly shown that THC impairs cognition, psychomotor function and actual driving performance in a dose related manner. The degree of performance impairment observed in experimental studies after doses up to 300 microg/kg THC were equivalent to the impairing effect of an alcohol dose producing a blood alcohol concentration (BAC) >/=0.05 g/dl, the legal limit for driving under the influence in most European countries. Higher doses of THC, i.e. >300 microg/kg THC have not been systematically studied but can be predicted to produce even larger impairment. Detrimental effects of THC were more prominent in certain driving tasks than others. Highly automated behaviors, such as road tracking control, were more affected by THC as compared to more complex driving tasks requiring conscious control. Epidemiological findings on the role of THC in vehicle crashes have sometimes contrasted findings from experimental research. Case-control studies generally confirmed experimental data, but culpability surveys showed little evidence that crashed drivers who only used cannabis are more likely to cause accidents than drug free drivers. However, most culpability surveys have established cannabis use among crashed drivers by determining the presence of an inactive metabolite of THC in blood or urine that can be detected for days after smoking and can only be taken as evidence for past use of cannabis. Surveys that established recent use of cannabis by directly measuring THC in blood showed that THC positives, particularly at higher doses, are about three to seven times more likely to be responsible for their crash as compared to drivers that had not used drugs or alcohol. Together these epidemiological data suggests that recent use of cannabis may increase crash risk, whereas past use of cannabis does not. Experimental and epidemiological research provided similar findings concerning the combined use of THC and alcohol in traffic. Combined use of THC and alcohol produced severe impairment of cognitive, psychomotor, and actual driving performance in experimental studies and sharply increased the crash risk in epidemiological analyses.
PMID: 14725950 [PubMed - indexed for MEDLINE]
Traffic Inj Prev. 2006 Jun;7(2):111-6. Links
Relationship between THC concentration in blood and impairment in apprehended drivers.
Khiabani HZ, Bramness JG, Bjørneboe A, Mørland J.
Norwegian Institute of Public Health, Division of Forensic Toxicology and Drug Abuse, Nydalen, Oslo, Norway. hassan.khiabani@fhi.no
OBJECTIVE: The most important psychoactive ingredient in cannabis, Delta (9)-tetrahydrocannabinol (THC) is one of the most frequently detected substances in blood samples from suspected impaired drivers in Norway. There is growing concern over possible links between the use of cannabis and increased risk of motor-vehicle crashes. Experimental studies have provided useful information on the role of THC and dose-effect relations with respect to psychomotor performance. The main purpose of the present study was to investigate whether a physician's judgment on impairment in a real-life setting among suspected drugged drivers, was related to blood THC concentration. METHODS: In Norway a police physician performs a clinical test for impairment (CTI) shortly after apprehension. The Norwegian Institute of Public Health analyze blood samples from all drivers suspected of driving under the influence of non-alcoholic drugs. In the present study 589 samples from approximately 30,000 cases of suspected drug impaired driving from the period 1997-99, contained THC as the only drug. In 456 of these cases a conclusion of the CTI was available. RESULTS: 230 (54%) drivers were considered not impaired and 226 (46%) impaired. Impaired drivers had higher blood THC concentration than the drivers who were judged as not impaired (median; 2.5 ng/mL (range; 0.3-45.3 ng/mL) vs 1.9 ng/mL (range; 0.32-24.8 ng/mL), (p < 0.05). Furthermore, drivers with blood THC concentrations above 3 ng/mL had an increased risk for being judged impaired compared to drivers with lower concentration ranges. CONCLUSION: The relationship between the concentration of THC in blood and risk of being assessed impaired found in this cross-sectional study of suspected drugged drivers, supports findings from previous experimental studies of concentration related effects of THC on psychomotor performance and driving skills.
PMID: 16854704 [PubMed - indexed for MEDLINE]
Can J Public Health. 2007 Jan-Feb;98(1):6-11. Links
The impact of cannabis on driving.
Bédard M, Dubois S, Weaver B.
Public Health Program, Lakehead University, Thunder Bay, ON. michel.bedard@lake-headu.ca
BACKGROUND: Cannabis is known to have detrimental effects on human performance and may also affect driving adversely. However, studies designed to examine this issue have provided equivocal findings. We set up this study to further determine the effect of cannabis on driving. METHODS: We used a cross-sectional, case-control design with drivers aged 20-49 who were involved in a fatal crash in the United States from 1993 to 2003; drivers were included if they had been tested for the presence of cannabis and had a confirmed blood alcohol concentration of zero. Cases were drivers who had at least one potentially unsafe driving action recorded in relation to the crash (e.g., speeding); controls were drivers who had no such driving action recorded. We calculated the crude and adjusted odds ratios (ORs) of any potentially unsafe driving action in drivers who tested positive for cannabis but negative for alcohol consumption. In computing for the adjusted OR, we controlled for age, sex, and prior driving record. RESULTS: Five percent of drivers tested positive for cannabis. The crude OR of a potentially unsafe action was 1.39 (99% CI = 1.21-1.59) for drivers who tested positive for cannabis. Even after controlling for age, sex, and prior driving record, the presence of cannabis remained associated with a higher risk of a potentially unsafe driving action (1.29, 99% CI = 1.11-1.50). CONCLUSION: Cannabis had a negative effect on driving, as would be predicted from human performance studies. This finding supports the need for interventions to decrease the prevalence of driving under the influence of cannabis, and indicates that further studies should be conducted to investigate the dose-response relationship between cannabis and safe driving.
PMID: 17278669 [PubMed - indexed for MEDLINE]