How common is driving under the influence of marijuana? Of driving under the influence of alcohol? Of driving under the influence of both at the same time?
To find out, self-reports of drivers age 16 to 25 were analyzed. The data came from the National Survey on Drug Use and Health from 2002 through 2014. That survey is conducted by the U.S. 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.
Between 2002 and 2014, 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.
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