TAKE THE FIRST STEP: DOES MARIJUANA AFFECT DRIVING ABILITY?

Q: There's a lot of information online about the effects of alcohol and
driving, but not much about marijuana.

Is there a certain amount of marijuana that can be smoked where it would
have virtually no measurable effect on one's ability to drive?

Is there a certain amount of time that could elapse between smoking
marijuana and getting behind the wheel where one would not be impaired? A:
Research has shown that marijuana can have some effect on one's driving
performance. More specifically, research has shown that people intoxicated
with marijuana may show some sway when driving in a straight line. However,
at the same time, research has shown that people high on marijuana are
aware that their performance is affected and they are able to compensate
for their difficulties. This is unlike individuals who are drunk and
believe that their driving abilities are not affected.

As a result, drunk drivers do not, and cannot, correct their judgment and
impairment, and their state of intoxication greatly affects their driving,
whereas those high on marijuana do show an ability to correct their impairment.

Researchers who have conducted these studies have also reported that the
driving impairment related to marijuana is subtle and may not generally be
seen in most driving situations. However, in an emergency situation, which
places a high demand on performance, it is possible that the use of
marijuana could lead to poorer judgment.

I also cannot say how long a person should wait after smoking marijuana
before driving because any effects would depend upon how much is smoked and
its potency.

Research, however, has shown that even when varying the dose of marijuana
taken, any driving impairment can last up to two hours. While I would never
recommend driving under the influence of marijuana, the research that I
have reviewed demonstrated that the driving impairment related to marijuana
is less dangerous than if the person was drunk.

However, it does cause some impairment, which could affect performance,
particularly in an emergency situation.

Taking the first step is the hardest part of all. Send questions about your
or someone else's behavior that could be the result of addiction or related
problems to: Take The First Step, c/o Essex County Newspapers, 32 Dunham
Road, Beverly, MA 01915; or send e-mail to michael_levy@cabhealth.org.
Questions will be answered in confidence by a clinical team led by Dr.
Michael Levy, director of clinical treatment services at CAB Health &
Recovery Services in Salem.