Years of untreated depression may lead to neurodegenerative levels of brain inflammation. That’s according to a first-of-its-kind study showing evidence of lasting biological changes in the brain for those suffering with depression for more than a decade.
The study findings are from the same research team
that originally identified a link between brain inflammation and
depression. Along with subsequent research, the findings have started to
change the thinking about depression treatments. Evidence is
increasingly pointing to the possibility that in addition to being a
biological disorder with immediate implications, over time depression
may also alter the brain in ways requiring different forms of treatment
than what's currently available.
This was a relatively small study of 80 participants; 25 had
untreated depression for more than 10 years, 25 for less than 10 years,
and 30 had never been diagnosed. All were evaluated with positron
emission tomography scans (PET scans) to locate a specific type of
protein that results from the brain’s inflammatory response to injury or
illness. Throughout the body, the brain included, the right amount of
inflammation protects us from disease and repairs us when we’re injured.
But too much inflammation leads to chronic illness, including heart
disease and potentially neurodegenerative diseases like Alzheimer’s and
Parkinson’s.
If long-term depression results in more inflammation, the researchers
expected to find more of the protein in the brains of those who’d
suffered from untreated depression the longest. And that’s exactly what
they found, with higher levels in a handful of brain areas, including
the prefrontal cortex, the brain area central to reasoning and other
“executive” functions, which is thought to be compromised by disorders
like depression.
If the results hold up (via more research with more participants),
this will prove to be an important finding adding evidence to the
argument that depression shares similarities with degenerative disorders
like Alzheimer’s, changing the brain in ways research-to-date hasn’t
fully grasped.
"Greater inflammation in the brain is a common response with degenerative brain diseases as they progress, such as with Alzheimer's disease and Parkinson's disease," said senior study author Dr. Jeff Meyer of the Centre for Addiction and Mental Health (CAMH) at the University of Toronto.
These findings build on a study published
in 2016 showing that patients with depression had higher levels
of C-Reactive Protein (CRP), another biological marker of inflammation,
throughout the body than those not suffering from the disorder. That was
an observational study looking for a link between depression and
inflammation (correlation not causation), but the results were
significant. After adjusting for several factors, those with depression
had CRP levels more than 30 percent higher than those without
depression.
What the research seems to be collectively indicating is that we may
need to change our thinking about depression and its effects. The
evidence affirms that depression truly is a biologically based disorder
of the brain, and left unchecked, it may run a degenerative course that
damages brain tissue in ways similar to other neurodegenerative
diseases. All of this places greater emphasis on the need to develop
more effective treatments and, as urgently, work toward removing the
stigma from those suffering.
ABOUT AUTHOR
David DiSalvo is a science and technology writer working at the intersection of cognition and culture.
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