Drug and Driving: A Compendium of Research Studies

Annotated Sources (cont'd)

New Zealand

45. Fergusson, D. M., and Horwood, L. J. (2001)

Cannabis use and traffic accidents in a birth cohort of young adults. Accident Analysis and Prevention 33: 703-711.


Survey of a cohort of young drivers

Type of study, population(s) and proportion tested

Birth cohort from New Zealand studied over the period of age 18-21 years

N=907, who reported driving a motor vehicle during that time, were included

Time period of study not mentioned

Drugs examined
  • Cannabis
  • Alcohol
Method of testing and medium used

Interviewed at age 21 about:

  • Cannabis use
  • Drink driving behaviours
Other dependent variables
  • Traffic accident involvement
  • Driver behaviours
  • Driver attitudes
  • Driver experience
  • Annual distance driven
  • Social, family, and individual factors
Findings (including statistical methods)

Used General Estimating Equation Model (regression)

Frequency of cannabis use was significantly related to rates of active (responsible) accidents (both before and after controlling for measures of driving experience)

Those who used cannabis more than 50 times per year had a 1.16 higher rate of active accidents

Cannabis use not related to passive (not responsible) accidents

Once accounting for confounding factors (in particular the significant correlation between cannabis use and risky/illegal driving behaviour), the OR dropped to .97, suggesting frequency of cannabis use was unrelated to active accidents

These findings were true even if cannabis frequency estimates were obtained from an informant and not directly from the individual

Researchers suggest that increased accident risk among cannabis users may be more related to the characteristics of the driver rather than the effects of cannabis on the driver behaviour

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