have discovered how chronic stress
and cortisol can
damage the brain
. A new study
reconfirms the importance of maintaining healthy brain structure and
connectivity by reducing chronic stress.
Neuroscientists at the University of California, Berkeley, have
found that chronic stress triggers long-term changes in brain structure and
function. Their findings might
explain why young people who are exposed to chronic stress early in life are
prone to mental problems such as anxiety and mood disorders later in life, as
well as learning difficulties.
It has long been established that stress-related illnesses, such as
stress disorder (PTSD)
trigger changes in brain structure, including differences in the volume of gray
matter versus white matter, as well as the and size and connectivity of the
amygdala. However, researchers are just beginning to understand exactly how
chronic stress creates long-lasting changes in brain structure which affect how
the brain functions.
In a series of revolutionary experiments, Daniela Kaufer, UC
Berkeley associate professor of integrative biology, and her colleagues,
discovered that chronic stress and elevated levels of cortisol can generate more
overproduction of myelin-producing cells and fewer neurons than normal. Kaufer
et al published their findings in
the February 11, 2014 issue of the journal Molecular Psychiatry.
Chronic Stress Changes Neural Networks
The "gray matter" of the brain is densely packed with nerve cell
bodies and is responsible for the brain's higher functions, such as thinking,
computing, and decision-making.
But gray matter is only half of the brain matter inside our heads—the other
half of brain volume is called white matter.
White matter is
comprised of axons, which create a network of fibers that interconnect neurons
and creates a communications network between brain regions. White matter gets
its name from the white, fatty myelin sheath that surrounds the axons and speeds
the flow of electrical signals between neurons and brain regions.
studied only one part of the brain, the hippocampus, but our findings could
provide insight into how white matter is changing in conditions such as schizophrenia
and PTSD,” Kaufer said. The hippocampus regulates memory
and emotions, and
plays a role in various emotional disorders and has been known to shrink under
extended periods of acute stress.
The researchers found that hardening wires, may be at the heart of
the hyper-connected circuits associated with prolonged stress. This
results in an excess of myelin—and too much white matter—in some areas of the
brain. Ideally, the brain likes to trim the fat of excess wiring through neural
pruning in order to maintain efficiency and streamlined communication within the
Cortisol Can Trigger Stem Cells to Malfunction
The ‘stress hormone’ cortisol is believed to create a domino effect
that hard-wires pathways between the hippocampus and amygdala in a way that
might create a vicious cycle by creating a brain that becomes predisposed to be
in a constant state of fight-or-flight.
Chronic stress has the ability to flip a switch in stem cells that
turns them into a type of cell that inhibits connections to the prefrontal
cortex, which would improve learning and memory, but lays down durable
scaffolding linked to anxiety, depression, and post-traumatic stress
Kaufer’s lab focused on neural stem cells in the hippocampus of the
brains of adult rats under acute or chronic stress. These stem cells were
previously thought to mature only into neurons or a type of glial cell called
However, the researchers found that chronic stress made stem cells
in the hippocampus mature into another type of glial cell called
an oligodendrocyte, which produces the myelin that sheaths
The finding suggests a key role for oligodendrocytes in long-term
and perhaps permanent changes in the brain that could set the stage for later
mental problems. Chronic stress decreases the number of stem cells that mature
into neurons and might provide an explanation for how chronic stress also
affects learning and memory, according to the researchers.
“Usually the brain doesn’t make much oligodendrocytes in adulthood
from those neural stem cells,” according to Kaufer. In fact, a recent study
suggested these cells were incapable of producing oligodendrocytes, which are
somewhat like a vine spreading out and wrapping around axons, both insulating
and supporting them.
Rats who have high levels of cortisol and chronic stress had fewer
neurons overall but a big increase in oligodendrocytes. By blocking the
equivalent of cortisol receptors, the researchers discovered the process was
tied to the stress hormone. “This was absolutely not what we were expecting to
find,” Kaufer said. “But those are always the best discoveries.”
this sheath is vital to human brains—myelin formation can be good or bad,
depending on time or place, according to Kaufer. This excessive sheathing may
have evolved to bolster the connection between the amygdala and hippocampus,
which would improve fight-or-flight responses during extended periods of threat
or attack… Unfortunately, in a modern world, chronic stress can hijack the
fight-or-flight system and backfire in a daily life in which you are not in
Conclusion: Plasticity Makes it Possible to “Sculpt” Your
Brain Throughout a Lifespan
Regular physical activity and mindfulness meditation
are two effective ways to reduce stress and lower cortisol. Although this study
doesn’t focus on the benefits of reducing cortisol, other research suggests that
making lifestyle choices that reduce stress and lower cortisol can improve brain
structure and connectivity.
For 5 simple ways to lower cortisol without drugs
check out my Psychology Today blog, “Cortisol:
Why “The Stress Hormone” Is Public Enemy No. 1.”
Daniela Kaufer is now conducting experiments to determine how
stress in infancy affects the brain’s white matter, and whether chronic
early-life stress decreases resilience later in
life. She also is looking at the effects of therapies, ranging from exercise to
drugs, that reduce the impact of stress and stress hormones.
Kaufer concludes that moderate or ‘good stress’—such as studying
hard for an exam or training to compete in the Olympic Games—can build stronger
circuitry and a more resilient brain. But acute, prolonged chronic stress wreaks
havoc. “You’re creating a brain that’s either resilient or very vulnerable to
mental disease, based on the patterning of white matter you get early in life,”
That said, the structure of your brain is constantly undergoing
changes through plasticity. Mindset, behavior, and chronic stress are never
fixed. The power of neuroplasticity makes it possible to change brain structure
and function throughout your lifespan. You can consciously make daily choices of
mindset and behavior that will improve the structure and connectivity of your
2012, Alex Schlegel from Dartmouth College published a study
that the adult brain can change for the better. "This work is contributing to a
that the brain stays this plastic organ throughout your life, capable of
change," Schlegel says.
"This flies in the face of all these traditional views that all
structural development happens in infancy, early in childhood,"
Schlegel says. "Now that we actually do have tools to watch a brain change, we
are discovering that in many cases the brain can be just as malleable as an
adult as it is when you are a child or an adolescent."
If you’d like to read more on this topic, check out
my Psychology Today blog posts:
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on The Athlete’s Way blog posts.