Epidemiology and traffic safety: culpability studies

Scientific proof that drugs capable of impairing skills required for safe driving has only come relatively recently, although the proof for ethanol (alcohol) came almost 40 years earlier. Instrumental in obtaining this evidence has been the use of culpability studies. These have provided an epidemiological basis to demonstrate an increased risk for use of amphetamine-type stimulants, cocaine and for those drivers showing recent use of cannabis through the presence of THC greater 5 ng/mL in blood. Significant increases in risk (through odd's ratio analysis) using this form of study has not been demonstrated for opiates. Benzodiazepines has provided consistent increases in risk in this form of analysis mainly because they are usually associated with other drugs (including alcohol). However, alcohol-drug and impairing drug-drug combinations generally show a very high culpability rate and are usually higher than one impairing drug alone. Culpability studies complement case control and other types of epidemiological evidence that links, or attempts to link, recent drug use with a vehicular crash.