We all know that aerobic exercise is an effective treatment
against depression. Yet, many people who would profit from more exercise do not
do it because they do not understand how physical exercise can impact a mental state.
Recent research has addressed the question.
Gretchen Reynolds reports in The New York Times:
Scientists
have also known that exercise seems to cushion against depression. Working out
somehow makes people and animals emotionally resilient, studies have shown.
But
precisely how exercise, a physical activity, can lessen someone’s risk for
depression, a mood state, has been mysterious.
How do scientists diagnose depression in mice?
Reynolds explains:
We
can’t ask mice if they are feeling cheerful or full of woe. Instead,
researchers have delineated certain behaviors that indicate depression in mice.
If animals lose weight, stop seeking out a sugar solution when it’s available —
because, presumably, they no longer experience normal pleasures — or give up
trying to escape from a cold-water maze and just freeze in place, they are
categorized as depressed.
Submit the mice to stress and they develop symptoms that
characterize depression.
But, isn’t that an interesting suggestion in and of itself?
Presumably, the mice do not have the mental means to do more than suffer the
stress. Human beings, however, do not necessarily turn stress into depression.
They can adapt to stress; they can manage stress; they can avoid it; they can
submit to it.
In other words, human beings have free will. Subjected to
stress they might withdraw from life and hole up in their rooms. But they can find other ways to manage and to overcome stress.
As for the scientific findings, Reynolds writes:
A
wealth of earlier research by these scientists and others had shown that
aerobic exercise, in both mice and people, increases the production within
muscles of an enzyme called PGC-1alpha. In particular, exercise raises levels
of a specific subtype of the enzyme known unimaginatively as PGC-1alpha1. The
Karolinska scientists suspected that this enzyme somehow creates conditions
within the body that protect the brain against depression.
She continues:
So the
scientists looked for which processes were being most notably intensified in
their PGC-1alpha1-rich mice. They found one in particular, involving a
substance called kynurenine that accumulates in human and animal bloodstreams
after stress. Kynurenine can pass the blood-brain barrier and, in animal
studies, has been shown to cause damaging inflammation in the brain, leading,
it is thought, to depression.
But in
the mice with high levels of PGC-1alpha1, the kynurenine produced by stress was
set upon almost immediately by another protein expressed in response to signals
from the PGC-1alpha1. This protein changed the kynurenine, breaking it into its
component parts, which, interestingly, could not pass the blood-brain barrier.
In effect, the extra PGC-1alpha1 had called up guards that defused the threat
to the animals’ brains and mood from frequent stress.
I will leave the brain science to others, but if exercise
can modify brain chemistry, perhaps changes in the way one deals with stress
can do so as well.
1 comment:
Very true as anyone who has done this would say. I'm not really prone to depression - in the larger sense - although days of physical and mental activity can definitely make me irritable, but having been someone who did aerobic exercise pretty regularly, biking and roller anywhere between 5 and 25 miles, it definitely has positive affects mentally as well as physically.
Even if it's not that much mileage, getting up and moving will have it's positive effect and the rebound is the more you do, the more you'll be able to do.
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