aerobic sessions (a bike ride or a hike in nature) and
more intense bursts. Chronic medium-intensity cardio
sessions (running on a treadmill for forty-five
minutes, for example) can actually increase cortisol.
We’ll see more on this in chapter 10.
Have somebody give you a massage (or pay for one
—never a bad investment!). A 2010 study out of
Cedars-Sinai Medical Center in Los Angeles found
that five weeks of Swedish massage significantly
reduced serum cortisol compared to controls who
underwent only “light touching.”
Practice deep breathing. Simple yet effective.
Exhaling activates the parasympathetic nervous
system, responsible for the body’s “rest-and-digest”
processes.It’s been known for some time that a chronic elevation
of cortisol compromises the brain’s supply of BDNF and
can atrophy vulnerable structures like the hippocampus,
even causing dendrites (the physical correlates of memories)
to recede.^26 This reinforces the negative aspects of stress,
since the hippocampus normally “vetoes” inappropriate
stress responses. Repeated stress therefore hurts your ability
to control stress, and this has been borne out in the research.
In mice that were subjected to chronic “social defeat”—the
equivalent of having a bully in the cage with them—their
memories suffered significantly. If the neural pathways
created by learning are akin to an ever-expanding set of
train tracks, it seemed as if those mice under duress were
having trouble laying down new tracks.