January 4, 2015
Photo Credit: KieferPix / Shutterstock.com
Barely a week goes by without a celebrity “opening up” about their
“battle with depression”. This, apparently, is a brave thing to do
because, despite all efforts to get rid of the stigma around depression,
it is still seen as some kind of mental and emotional weakness.
But
what if was nothing of the sort? What if it was a physical illness that
just happens to make people feel pretty lousy? Would that make it less
of a big deal to admit to? Could it even put a final nail in the coffin
of the idea that depression is all in the mind?
According to a
growing number of scientists, this is exactly how we should be thinking
about the condition. George Slavich, a clinical psychologist at the
University of California in Los Angeles, has spent years studying
depression, and has come to the conclusion that it has as much to do
with the body as the mind. “I don’t even talk about it as a psychiatric
condition any more,” he says. “It does involve psychology, but it also
involves equal parts of biology and physical health.”
The
basis of this new view is blindingly obvious once it is pointed out:
everyone feels miserable when they are ill. That feeling of being too
tired, bored and fed up to move off the sofa and get on with life is
known among psychologists as sickness behaviour. It happens for a good
reason, helping us avoid doing more damage or spreading an infection any
further.
It also looks a lot like depression. So if people with
depression show classic sickness behaviour and sick people feel a lot
like people with depression – might there be a common cause that
accounts for both?
The answer to that seems to be yes, and the
best candidate so far is inflammation – a part of the immune system that
acts as a burglar alarm to close wounds and call other parts of the
immune system into action. A family of proteins called cytokines sets
off inflammation in the body, and switches the brain into sickness mode.
Both cytokines and inflammation
have been shown to rocket during depressive episodes,
and – in people with bipolar – to drop off in periods of remission.
Healthy people can also be temporarily put into a depressed, anxious
state when given a vaccine that causes a spike in inflammation.
Brain imaging studies of people injected with a typhoid vaccine found that this might be down to changes in the parts of the brain that process reward and punishment.
There
are other clues, too: people with inflammatory diseases such as
rheumatoid arthritis tend to suffer more than average with depression;
cancer patients given a drug called interferon alpha, which boosts their
inflammatory response to help fight the cancer, often become depressed
as a side-effect.
As evidence like this continues to stack up,
it’s not surprising that some people have shifted their attention to
what might be causing the inflammation in the first place.
Turhan Canli of Stony Brook University in New York thinks infections are the most likely culprit, and
even goes as far as to say that we should rebrand depressionas an infectious – but not contagious – disease.
Others
aren’t willing to go that far, not least because infection is not the
only way to set off inflammation. A diet rich in trans fats and sugar
has been shown to promote inflammation, while a healthy one full of
fruit, veg and oily fish helps keep it at bay. Obesity is another risk
factor, probably because body fat, particularly around the belly, stores
large quantities of cytokines.
Add this to the fact that stress,
particularly the kind that follows social rejection or loneliness, also
causes inflammation, and it starts to look as if depression is a kind of
allergy to modern life – which might explain its spiralling prevalence
all over the world as we increasingly eat, sloth and isolate ourselves
into a state of chronic inflammation.
If that’s the case,
prevention is probably the place to start. It’s not a great idea to turn
off inflammation entirely, because we need it to fend off infections,
says Slavich, but “lowering levels of systemic inflammation to
manageable levels is a good goal to have”.
The good news is that
the few clinical trials done so far
have found that adding anti-inflammatory medicines to antidepressants
not only improves symptoms, it also increases the proportion of people
who respond to treatment, although more trials will be needed to confirm
this.
There is also some evidence that omega 3 and
curcumin, an extract of the spice turmeric,
might have similar effects. Both are available over the counter and
might be worth a try, although as an add-on to any prescribed treatment –
there’s definitely not enough evidence to use them as a replacement.
In
between five to 10 years, says Carmine Pariante, a psychiatrist at
Kings College London, there may be a blood test that can measure
inflammation in people with depression so that they can be treated
accordingly. Researchers have already come up with a simple finger-prick
test that reliably measures inflammation markers in a single drop of
blood.
And as for the stigma – could it really be killed off by
shifting the blame from the mind to the body? Time will tell. This is
not the first time that depression has been linked to a physical
phenomenon, after all.
A recent survey found that despite wider awareness of the theory
that “chemical imbalances” in the brain cause depression, this has done
nothing to reduce stigma; in fact, it seemed to make matters worse.
This
time, though, the target is not any kind of brain or mind-based
weakness but a basic feature of everyone’s body that could strike anyone
down given the right – or wrong – turn of events. And if that doesn’t
inspire a greater sympathy and understanding, then nothing will.
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