New research shows that deep brain stimulation can tackle
treatment-resistant depression. Stimulating a brain area called the
orbitofrontal cortex led to "significant" improvements in mood for
people with moderate to severe depression.
Using DBS to target certain key
areas may relieve symptoms of severe depression.
Major depressive disorder affects over 16 millionadults per
year in the United States and is the "leading cause of disability worldwide."
A significant proportion of people who are living with
major depression do not get any relief from existing
treatments.
In fact, up to 30 percent of those affected by depression
have an intractable form of the condition.
Recently, deep brain stimulation (DBS) has
emerged as a potential therapy that may succeed where other treatments have
failed.
In DBS, specialists surgically implant stimulating
electrodes in the brain to send electrical currents to targeted areas.
In the new study, Dr. Eddie Chang and his colleagues used
DBS in 25 people who had symptoms of depression. They report their findings in the
journal Current Biology.
Dr. Chang is also a professor of neurosurgery at the
University of California San Francisco (UCSF).
Studying depression and key brain
areas
Dr. Chang explains what made the researchers focus on the
orbitofrontal cortex in this study. The area "has been called one of the
least understood regions in the brain," he reports, "but it is richly
connected to various brain structures linked to mood, depression, and decision-making,
making it very well positioned to coordinate activity between emotion and
cognition."
The team had access to a clinic that specializes in epilepsy. People with epilepsy have electrodes surgically
implanted in their brains as part of routine preparation for surgery.
For this study, Dr. Chang and team recruited 25 participants
with epilepsy who also had mild to severe depression.
With the electrodes already in place, the participants
reported how they were feeling a few times per day using an app. This enabled
the researchers to link changes in brain activity with different moods,
focusing on the brain area that was most involved in depression and also
accessible with DBS.
The scientists also used mild electrical stimulation on
different brain regions and asked participants to say how it affected their
mood using specific keywords.
Afterward, they — with the help of a specific piece of
software — quantified and analyzed the words that the volunteers had used.
DBS led to a 'naturally positive
mood'
The study revealed that, while stimulating most brain areas
had no effect on the participants' mood, 3 minutes of stimulating the lateral orbitofrontal
cortex led to significant improvements.
The successful results were only seen among those with
moderate to severe depression; there was no effect in people with mild
depression symptoms.
Study co-author Kristin Sellers, Ph.D. — who is a
postdoctoral researcher in Dr. Chang's laboratory — reports on the results.
"Patients said things like 'Wow, I feel better,' 'I feel less anxious,' 'I
feel calm, cool, and collected.'"
"And just anecdotally, you could see the improvements
in patients' body language. They smiled, they sat up straighter, they started
to speak more quickly and naturally."
The patterns of brain activity also supported these
noticeable improvements in mood. The authors note that the participants' brain
activity after the stimulation resembled the brain activity that occurred when
the volunteers reported feeling naturally good.
Dr. Vikram Rao, Ph.D. — an assistant professor of neurology
at UCSF and the study's first author — explains what these findings mean.
"These
[...] observations suggest that stimulation was helping patients with serious
depression experience something like a naturally positive mood state, rather
than artificially boosting mood in everyone."
Dr. Vikram Rao
"This is in line with previous observations," he
adds, "that [orbitofrontal cortex] activity is elevated in patients with
severe depression and suggests electrical stimulation may affect the brain in a
way that removes an impediment to positive mood that occurs in people with
depression."
The researchers note, however, that more studies will be
needed before they can conclude that stimulating the orbitofrontal cortex
improves mood in the long-term.
"The more we understand about depression at this level
of brain circuitry, the more options we may have for offering patients
effective treatments with a low risk of side effects," says study
co-author Heather Dawes, Ph.D.
"Perhaps by understanding how these emotion circuits go
wrong in the first place, we can even one day help the brain 'unlearn'
depression."
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