WASHINGTON - Sure, exercise is good for your waistline, your heart, your
bones - but might it also help prevent addiction to drugs or alcohol?
There are some tantalizing clues that physical activity might spur changes in
the brain to do just that. Now the U.S. government is beginning a push for hard
research to prove it.
This is not about getting average people to achieve the so-called runner's high,
a feat of pretty intense athletics.
Instead, the question is just how regular physical activity of varying intensity
- dancing, bicycling, swimming, tae kwan do - might affect mood, academic
performance, even the very reward systems in the brain that can get hijacked by
substance abuse.
What first caught the attention of National Institute on Drug Abuse chief Dr.
Nora Volkow: A study found tweens and teens who reported exercising daily were
half as likely to smoke as their sedentary counterparts, and 40 per cent less
likely to experiment with marijuana.
Volkow knows - from her own almost 10-kilometre daily runs and from her
scientific experiments - that the brain literally likes physical activity.
Exercise seems to invigorate neurochemicals that sense and reinforce pleasure.
"In children, it's innate," she notes. "Children want to move."
But the nation's children are becoming more sedentary, as illustrated by the
obesity epidemic, "screen time" replacing outdoor play and a drop in school
phys-ed. And as youngsters approach adolescence, the run around the yard that
used to be fun too often becomes a chore - the dreaded jog around the school
track or the nagging to get off the couch. The sedentary teen turns into the
sedentary adult.
"Why do we lose the ability to experience pleasure from physical activity?" asks
Volkow.
Last week she brought more than 100 specialists in exercise and neurobiology to
a two-day conference to explore physical activity's potential in fighting
substance abuse, and announced $4 million in new research grants to help.
Drug treatment programs often include exercise, partly to keep people distracted
from their cravings, but there's been little formal research on the effects.
The best evidence: Brown University took smokers to the gym three times a week
and found adding the exercise to a smoking-cessation program doubled women's
chances of successfully kicking the habit. The quitters who worked out got an
extra benefit: They gained half as much weight as women who managed to quit
without exercising, says lead researcher Dr. Bess Marcus.
She now is working with the YMCA on a larger, NIDA-funded study to prove the
benefit.
Marcus cautions that people trying to kick an addiction have a powerful
incentive to exercise. Could that possibly translate into prevention? Among the
clues:
-Rats were less likely to ingest amphetamines if their cages had running wheels,
suggesting exercise stimulated a reward pathway in the brain to leave them less
vulnerable to the drug's rush.
-In people, exercise acts as a mild antidepressant and relieves stress.
Depression, anxiety and stress increase risk of alcoholism, smoking or drug
abuse.
-Volkow is intrigued that attention deficit disorder and obesity both involve
problems with the brain chemical dopamine, one system that drugs hijack to
create addiction.
-Baby monkeys who don't play enough in childhood have problems controlling
aggression when they're older. The most aggressive tend to have defects
involving the feel-good brain chemical serotonin - and binge-drink when
researchers offer them alcohol.
-Back to rats, physical activity increases production of growth factors and stem
cells in key brain regions important for learning and mood; increases formation
of blood vessels; and strengthens communication networks between brain cells.
Together, that's far too little research to know if exercise really matters for
substance abuse, scientists at the National Institutes of Health meeting
cautioned.
But, a few studies of school-age children suggest physical activity predicts
better performance on math, verbal and other tests - and better school
performance in turn is linked to lower risk for substance abuse.
And getting sedentary seniors moving improves brain function - research aimed at
preventing dementia, not drug abuse, although the improvement is in an area that
in younger people is linked to risky decision-making.
A caveat: If your own youth includes memories of parties with beer-guzzling
athletes, well, the research concurs. A major study that tracks adolescent risk
behaviours found that by 12th grade, exercise offers no protection against
binge-drinking.
"Now the kids who exercise the most actually drink the most," says Dr. Lloyd
Johnston of the University of Michigan. It may have to do with the celebratory
nature of team sports, or getting revved for college - or, other researchers
suggested, even that competition is to blame.
