How common is driving under the influence of marijuana? Of driving under the influence of alcohol? Or of driving under the influence of marijuana, alcohol, and both at the same time?

Study

To find out, researchers studied self-reports of drivers age 16 to 25. The data came from the National Survey on Drug Use and Health over a period of 12 years. That survey is conducted by the US Substance Abuse and Mental Health Services Administration (SAMSHA).

The incidence of driving under the influence of alcohol alone dropped 59% among those age 16-20. It fell 38% among those age 21-25.

Driving under the influence of both alcohol and marijuana dropped 39% among those age 16-20. It declined 52% among those age 21-25.

The prevalence of driving under the influence of marijuana alone fell 18%, but only among drivers age 16-20.

During the 12 years, the incidence of driving under the influence of alcohol, marijuana, and both generally dropped greatly.

The effects of alcohol and marijuana on driving skills is additive. Together, they have much greater effect than separately. This suggests the need for greater concern about reducing driving while under the influence of both at the same time.

Resources: Influence of Marijuana, Alcohol, and Both

Readings

Bedard, M., et al. The impact of cannabis on driving.  Canad J Pub Health, 98(1),  6-11.

Hanson, D. The Effects of Substances on Driving. In: Miller, Peter (Ed). Principles of Addiction: Comprehensive Addictive Behaviors and Disorders. Amsterdam: Elsevier.

Ramaekers, J., et al. Marijuana, alcohol and actual driving performance.  Hum. Psychopharm. Clin. Exp., 15, 551-8.

Sewell. R., et al.  The Effect of Cannabis Compared with Alcohol on Driving.  Am J Addict., 18(3),  185-93.

Source

Azofeila, A., et al. Driving under the influence of alcohol, marijuana,  and alcohol and marijuana combined among persons aged 16-25 years. Morbid Mort Weekly Rep, 64(48), 1325-9.

Note

This site gives no advice. Please see your doctor for that.