Is Depression A Physical Illness? Unravelling The Inflammation Hypothesis

Is Depression A Mental Or Physical Illness? Unravelling The Inflammation Hypothesis

Most people feel down, tired and inactive when they’re injured or ill. This “sickness behaviour” is caused by the activation of the body’s immune response. It’s the brain’s way of conserving energy so the body can heal.

This immune response can also occur in people with depression. This has prompted some researchers and clinicians to hypothesise that depression is actually a side effect of the inflammatory process.

But while there may be a connection between inflammation and depression, one doesn’t necessarily lead to the other. So it’s too simplistic to say depression is a physical, rather than a psychiatric, illness.

The Inflammation Hypothesis

University of California clinical psychologist and researcher George Slavich is one of the key recent proponents of depression as a physical illness. He hypothesises that social threats and adversity trigger the production of pro-inflammatory “cytokines”. These are messenger molecules of the immune system that play a critical role in orchestrating the host’s response to injury and infection.

This inflammatory process, Slavich argues, can initiate profound behavioural changes, including the induction of depression.

The idea that the activation of the immune response may trigger depression in some people is by no means a new one. Early descriptions of post-influenza depression appeared in the 19th century in the writings of English physician Daniel Tuke.

But it was not until the 1988 seminal paper, published by veterinarian Benjamin Hart, that the phenomenon of acute “sickness behaviour” caught the interest of the scientific community.

Hart described his detailed observations of the “behaviour of sick animals”. During acute infection, and in response to fever, the animals sought sleep, lost their appetite, showed a reduction in activity, grooming and social interactions, as well as showing signs of “depression”.

Just like the immune response itself, these changes reflect an evolved survival strategy that shifts priorities toward energy conservation and recovery.

Putting The Theory Into Practice

Cytokine-induced sickness behaviour has subsequently been studied as an example of communication between the immune system and the brain.


 Get The Latest By Email

Weekly Magazine Daily Inspiration

The behavioural changes during sickness resemble those associated with depression, so it didn’t take long for researchers to make a connection between the phenomenon of sickness behaviour and mental disorders.

Such speculation was strengthened by research showing that depressive states can be experimentally induced by administering cytokines and other immunogenic agents (such as vaccines) that cause an inflammatory response.

Depression is frequently associated with inflammatory illnesses such as heart disease and rheumatoid arthritis. It’s also a side effect of treatment with cytokines to enhance the immune system.

Over recent decades, researchers have made progress in understanding how inflammation may impact on the activity of signalling pathways to and from the brain, as well as on the functioning of key neural systems involved in mood regulation.

But There’s Not Always A Link

From the available evidence it’s clear, however, that not everyone who suffers from depression has evidence of inflammation. And not all people with high levels of inflammation develop depression.

Trajectories of depression depend on a complex interplay of a spectrum of additional risk and resilience factors, which may be present to varying degrees and in a different combination in any individual at different times. These factors include the person’s:

genetic vulnerabilities affecting the intensity of our inflammatory response

* other medical conditions

* acquired hyper-vigilance in the stress response systems due to early life trauma, current adversities, or physical stressors

* coping strategies, including social support

* health behaviours, such as sleep, diet and exercise.

Implications For Treatment

In line with the notion that inflammation drives depression, some researchers have already trialled the effectiveness of anti-inflammatory therapy as a treatment for depression.

While some recipients (such as those with high levels of inflammation) showed benefit from the treatment, others without increased inflammation did not. This supports the general hypothesis.

However, in our desire to find more effective treatments for depression, we should not forget that the immune response, including inflammation, has a specific purpose. It protects us from infection, disease and injury.

Cytokines act at many different levels, and often in subtle ways, to fulfil their numerous roles in the orchestration of the immune response. Undermining their vital role could have negative consequences.

Mind Versus Body

The recent enthusiasm to embrace inflammation as the major culprit in psychiatric conditions ignores the reality that “depression” is not a single condition. Some depressive states, such as melancholia, are diseases; some are reactions to the environment; some are existential; and some normal.

Such separate states have differing contributions of biological, social and psychological causes. So any attempt to invoke a single all-explanatory “cause” should be rejected. Where living organisms are concerned it is almost never that simple.

In the end, we cannot escape the reality that changes must occur at the level of the brain, in regions responsible for mood regulation, for “depression” to be experienced.

About The AuthorsThe Conversation

Ute Vollmer-Conna is Associate Professor, School of Psychiatry at UNSW Australia. She is an internationally recognized leader in multidisciplinary research examining the acute sickness response to common infections, and post-infective syndromes of chronic fatigue and depression.

Gordon Parker is Scientia Professor at UNSW Australia. He is an expert in mood disorders, founder of the Black Dog Institute

This article was originally published on The Conversation. Read the original article.

You May Also Like

follow InnerSelf on

facebook icontwitter iconyoutube iconinstagram iconpintrest iconrss icon

 Get The Latest By Email

Weekly Magazine Daily Inspiration

AVAILABLE LANGUAGES

enafarzh-CNzh-TWdanltlfifrdeeliwhihuiditjakomsnofaplptroruesswsvthtrukurvi

INNERSELF VOICES

Lunar eclipse, May 12, 2022
Astrological Overview and Horoscope: May 23 - 29, 2022
by Pam Younghans
This weekly astrological journal is based on planetary influences, and offers perspectives and…
05 21 rewilding the imagination in dangerous times 5362430 1920
Rewilding the Imagination in Dangerous Times
by Natureza Gabriel Kram
In a world that often seems intent on destroying itself, I find myself curating beauty -- the kind…
group of multi-racial individuals standing for a group photo
Seven Ways You Can Show Respect to Your Diverse Team (Video)
by Kelly McDonald
Respect is profoundly meaningful, but costs nothing to give. Here are ways you can demonstrate (and…
elephant walking in front of a setting sun
Astrological Overview and Horoscope: May 16 - 22, 2022
by Pam Younghans
This weekly astrological journal is based on planetary influences, and offers perspectives and…
photo of Leo Buscaglia from cover of his book: Living, Loving and Learning
How to Change Someone's Life in a Few Seconds
by Joyce Vissell
My life was changed dramatically when someone took that second to point out my beauty.
a composite photograph of a total lunar eclipse
Astrological Overview and Horoscope: May 9 - 15, 2022
by Pam Younghans
This weekly astrological journal is based on planetary influences, and offers perspectives and…
05 08 developing compassionate thinking 2593344 completed
Developing Compassionate Thinking Towards Self and Others
by Marie T. Russell, InnerSelf.com
When people speak of compassion, they mostly are referring to having compassion for others... for…
a man writing a letter
Writing the Truth and Allowing the Emotions to Flow
by Barbara Berger
Writing things down is a good way to practice truth telling.
father holding son in his arms and walking down the road
Seeking Freedom From or Freedom To?
by Marie T. Russell
Freedom is such a powerful word, yet do we really know what it means? For years freedom was tied to…
Why It's Important To "Be Selfish" and Keep Your Energy High
Why It's Important To "Be Selfish" and Keep Your Energy High
by Barbara Berger
When I coach people to find and follow their Inner Compass, they often ask, "But isn't it selfish…
The Real Source Of The Energy Shortage Lies In Unexpressed Potential
The Real Energy Shortage Lies In Unexpressed Potential
by Eileen Workman
Analysts tell us that the pending collision between humanity's growing energy needs and the energy…

MOST READ

eyes predict health 4 9
What Your Eyes Reveal About Your Health
by Barbara Pierscionek, Anglia Ruskin University
Scientists at the University of California, San Diego, have developed a smartphone app that can…
rebuilding environment 4 14
How Native Birds Are Returning To New Zealand’s Restored Urban Forests
by Elizabeth Elliot Noe, Lincoln University et al
Urbanisation, and the destruction of habitat it entails, is a major threat to native bird…
The Story Of Suffering And Death Behind Ireland’s Abortion Ban And Subsequent Legalization
The Story Of Suffering And Death Behind Ireland’s Abortion Ban And Subsequent Legalization
by Gretchen E. Ely, University of Tennessee
If the U.S. Supreme Court overturns Roe v. Wade, the 1973 decision that legalized abortion in the…
how much sleep you need 4 7
How Much Sleep You Really Need
by Barbara Jacquelyn Sahakian, University of Cambridge, et al
Most of us struggle to think well after a poor night’s sleep – feeling foggy and failing to perform…
benefits of lemmon water 4 14
Will Lemon Water Detox Or Energize You?
by Evangeline Mantzioris, University of South Australia
If you believe anecdotes online, drinking lukewarm water with a splash of lemon juice is…
trusting societies are happy 4 14
Why Trusting Societies Are Overall Happier
by enjamin Radcliff, University of Notre Dame
Human beings are social animals. This means, almost as a matter of logical necessity, that humans’…
economy 4 14
5 Things That Economists Know, But Sound Wrong To Most Other People
by Renaud Foucart, Lancaster University
A curious thing about our profession is that when we academic economists largely agree with each…
learning to pay attention 4 14
These Strategies And Life Hacks Can Help Anyone With Attention Problems
by Rob Rosenthal, University of Colorado
Because of the steady stream of negative feedback people receive about their productivity,…

New Attitudes - New Possibilities

InnerSelf.comClimateImpactNews.com | InnerPower.net
MightyNatural.com | WholisticPolitics.com | InnerSelf Market
Copyright ©1985 - 2021 InnerSelf Publications. All Rights Reserved.