|
 But chronic cannabis consumption starting later in life was not
associated with worse performance behind the wheel, Dr. Staci A.
Gruber, director of the Marijuana Investigations for Neuroscientific
Discovery (MIND) Program at McLean Hospital in Belmont,
Massachusetts, and her colleagues found.
"This is not surprising to us at all, and really just underscores
what we've already seen," Gruber told Reuters Health in a phone
interview. "Earlier onset of the use of any substance is more likely
to confer a greater risk of problems later."
Eleven U.S. states and Washington, DC, have legalized adult
marijuana use, while 33 states have medical marijuana programs,
Gruber and her team note in their report in the journal Drug and
Alcohol Dependence. Research on cannabis and driving has focused on
acute intoxication, with some studies but not others showing that
people drive more slowly when high. Studies looking at cannabis
intoxication and car crashes have also had mixed results.
To investigate whether heavy cannabis use might have residual
effects on driving performance, the authors had 17
non-cannabis-using healthy participants and 28 chronic cannabis
users complete a 10-minute, 4.2-mile driving simulation test. The
cannabis users were instructed to abstain for at least 12 hours
beforehand.
Participants ranged in age between about 18 and 28 years old. Half
of the cannabis-using group had begun heavy use before age 16.
The early-use group had more crashes, missed more stop signs and red
lights, and spent more time driving over the speed limit than the
control group. However, there were no differences in any measure of
driving performance between the participants who started using
cannabis when they were older and the control group of non-users.
In fact, the analysis found that self-reported impulsivity accounted
for almost all of the difference in results between the early-use
and control groups.
[to top of second column] |
"Early exposure to cannabis results in difficulties with different
types of cognitive tasks. It really does come down to a question of
age of onset of exposure," Gruber said. "Individuals who are using
cannabis on a regular, consistent basis, heavy cannabis users, prior
to age 16 appear to look different from those who start using heavy
amounts of cannabis after age 16."
The study wasn't designed to determine whether or how early cannabis
use might influence impulsivity or the reverse, nor can it say how
either of these traits may affect driving skills later in life.
While pushing adolescents to abstain from cannabis and other
substances isn't effective, Gruber noted, recommending that they
wait could be a more useful approach. "It's not a message of 'just
say no,' it's a message of 'just not yet,'" Gruber said. "We're not
saying never, we're saying right now you're in a period of
vulnerability, why not give yourself a little more time."
The study "raises almost more questions than it answers," Dr. Thomas
G. Brown, an addiction researcher at the Douglas Mental Health
University Institute and McGill University in Montreal, told Reuters
Health in a phone interview.
Adolescents who are prone to risky behavior may be more likely to
become heavy pot smokers, and these personality traits may also make
them riskier drivers, explained Brown, who wasn't involved in the
study. "We don't know from this study whether what we're seeing is
cannabis use, or the consequence of these personality features that
promote risk taking of all sorts."
SOURCE: https://bit.ly/2FWzuD4 Drug and Alcohol Dependence, online
January 14, 2020.
[© 2020 Thomson Reuters. All rights
reserved.] Copyright 2020 Reuters. All rights reserved. This material may not be published,
broadcast, rewritten or redistributed.
Thompson Reuters is solely responsible for this content.
 |
