Driving behavior under the influence of cannabis or cocaine.

OBJECTIVE: The purpose of this study is first to describe perceptions of driving under the influence of cannabis or cocaine among clients in treatment and, second, to assess whether these perceptions are related to the frequency of driving under the influence of cannabis or cocaine.

METHODS: A questionnaire was administered to clients in treatment for abuse of either cocaine or cannabis, many of whom also had a problem with alcohol; additional groups of clients consisted of those in smoking cessation and gambling programs (N = 1021). Open-ended and close-ended questions were used to assess self-reported effects of cannabis or cocaine on driving and frequency of driving under the influence of cannabis, cocaine, or alcohol.

RESULTS: Two dimensions of driving behavior under the influence of cocaine or cannabis were found in both qualitative and quantitative analyses: 1) physical effects and 2) reckless styles of driving. Common physical effects for both drugs were heightened nervousness, greater alertness, and poorer concentration. In terms of driving behavior, cautious or normal driving was commonly reported for cannabis, whereas reckless or reduced driving ability was frequently reported for cocaine. When comparing negative physical effects and reckless style of driving with frequency of driving under the influence of cannabis or cocaine, increased negative physical effects from cannabis were inversely related to frequency of driving under the influence of cannabis (p = .001), but other relationships were not significant.

CONCLUSIONS: The findings indicate that both cannabis and cocaine have detrimental but different effects on driving. The negative physical effects of cannabis may reduce the likelihood of driving under the influence of cannabis.